Review of Devonian-Carboniferous Boundary sections in the Rhenish Slate Mountains (Germany)

Abstract

Thirty Devonian-Carboniferous Boundary sections of the Rhenish Slate Mountains and adjacent subsurface areas are reviewed with respect to litho-, event, conodont, ammonoid, sequence, and chemostratigraphy. In the interval from the base of the uppermost Famennian (Wocklum Beds, Wocklumian) to the base of the middle Tournaisian (base Lower Alum Shale), 11 conodont and 16 ammonoid (sub)zones are distinguished. The terminology of the Hangenberg Crisis Interval is refined, with an overall regressive Crisis Prelude below the main Hangenberg Extinction, which defines the base of the transgressive Lower Crisis Interval (Hangenberg Black Shale). The glacigenic and regressive Middle Crisis Interval (Hangenberg Shale/Sandstone) is followed by the overall transgressive Upper Crisis Interval that can be subdivided into three parts (I to III) with the help of conodont stratigraphy (upper costatus-kockeli Interregnum = upper ckI, Protognathodus kockeli Zone, and lower part of Siphonodella (Eosiphonodella) sulcata s.l./Pr. kuehni Zone). Protognathodus kockeli includes currently a wide range of forms, which variabilities and precise ranges need to be established before a precise GSSP level should be selected. Returning to its original definition, the former Upper duplicata Zone is re-named as Siphonodella (S.) mehli Zone. It replaces the S. (S.) jii Zone, which is hampered by taxonomic complications. The S. (S.) quadruplicata Zone of Ji (1985) is hardly supported by Rhenish data. The entry of typical S. (S.) lobata (M1) characterises an upper subdivision (subzone) of the S. (S.) sandbergi Zone; the new S. (S.) lobata M2 enters much earlier within the S. (S.) mehli Zone. The ammonoid-defined base of the Wocklum-Stufe (Upper Devonian = UD VI) begins with the Linguaclymenia similis Zone (UD VI-A1). The oldest S. (Eosiphonodella) enter within the Muessenbiaergia bisulcata Zone (UD VI-A2). The traditional Parawocklumeria paradoxa Zone of Schindewolf (1937) is divided into successive P. paprothae (VI-C1), P. paradoxa (VI-C2), and Mayneoceras nucleus (VI-C3) Subzones. In the lower Tournaisian (Lower Carboniferous = LC I), the Gattendorfia subinvoluta Zone is subdivided into G. subinvoluta (LC I-A2) and “Eocanitesnodosus (LC I-A3) Subzones. The Paprothites dorsoplanus Zone (LC I-B) can be divided into Pap. dorsoplanus (LC I-B1) and Paragattendorfia sphaeroides (LC I-B2) Subzones. Potential subdivisions of the Pseudarietites westfalicus (LC I-C) and Parag. patens Zones (LC I-D) are less distinctive. The unfossiliferous or argillaceous upper part of the Hangenberg Limestone and the overlying Lower Alum Shale Event Interval remain regionally unzoned for ammonoids.

Introduction

The Rhenish Slate Mountains, especially the northern and eastern Sauerland in the east of the river Rhine, are the most important of the classical regions for the study of the Devonian-Carboniferous Boundary (DCB) and of the global mass extinction interval that is now known as Hangenberg Crisis (e.g. Kaiser et al. 2015). Following a proposal by Paeckelmann and Schindewolf (published in 1937), the DCB type section was defined during the Second Heerlen Congress in 1935 in a railway cut near Oberrödinghausen. This was the first international chronostratigraphic boundary that was established at all. Unfortunately, it had to be discarded when a hiatus was discovered right at the chosen boundary level (Alberti et al. 1974). During the following search for a new stratotype, many old and new lateral sections were investigated in detail. Results were published in a series of monographs, review papers, and field guidebooks. Important summaries are, for example, Stoppel (1977), Paproth and Streel (1982, 1984), Paproth (1986), Paproth et al. (1986b), Clausen et al. (1989a), Streel et al. 1993, Becker et al. (1993), Korn et al. (1994a), Korn (2002), Hartenfels et al. (2016), and Becker et al. (2016b). There is a flood of individual papers (e.g. many contributions by D. Korn, F.W. Luppold, and co-authors), which are fully referenced in the individual section descriptions. These form the fundament of our review, which includes a smaller amount of unpublished information. Since research is ongoing, this paper will be completed soon by forthcoming publications. For example, a new study will provide details of the currently best Rhenish DCB section at the Borkewehr near Wocklum (northern Sauerland). A palaeogeographical overview was given by Paproth et al. (1986a), with recent updates by Koltonik et al. (2018).

For details concerning the global, first order Hangenberg Crisis or mass extinction, the reader is referred to the review by Kaiser et al. (2015). Becker et al. (2016a) summarised the DCB bio- and event stratigraphy, with the Rhenish succession as a sort of “standard reference” for global correlations. This approach is elaborated here by the introduction of a new formal subdivision and nomenclature for the distinctive intervals of the Hangenberg Crisis. We supply a summary of Rhenish DCB conodont and ammonoid zones, with new subzones, and the evidence they are based on. Due to the considerable number of Rhenish DCB sections and the wealth of literature, our review will exploit the extensive published evidence by quoting for each section all relevant papers, and by focusing on the staged entries (FADs, local FODs) and disappearances (LADs/local LODs) of stratigraphically relevant taxa and rare/unusual taxon occurrences. For detailed data on sedimentology and the complete faunal records, the reader should survey the quoted papers. In the section discussions, we emphasise aspects that are of especial importance for the current DCB revision and selection of a future GSSP level and section. Since significant parts of the reviewed information have previously been published in German, our paper aims to recycle the incredibly rich Rhenish DCB record for a wide international audience.

Abbreviations and repository

DCB = Devonian-Carboniferous Boundary, FAD/FOD = first appearance (global) and occurrence (local) datum, LAD/LOD = last appearance (global) and occurrence (local) datum, LC = Lower Carboniferous, Tn = Tournaisian, UD = Upper Devonian; for the ammonoid zonal key see Becker (1996) and Fig. 1.

Fig. 1
figure1

Correlation of chrono-, litho- bio-, and event stratigraphy around the Devonian-Carboniferous Boundary, showing both zonal index taxa (in bold) and important auxiliary marker species [in brackets]. The ammonoid zonal key follows, with further subdivision, the scheme of Becker (1996); m.T. = middle Tournaisian, (quad.) = approximate level of former Siphonodella (S.) quadruplicata Zone, SLBS = Stockum Level Black Shales, sdst. = sandstone. s.l. = sensu lato (in a wide taxonomic sense) For (sub)generic abbreviations see main text

Lithostratigraphic units: HBS = Hangenberg Black Shale, HS = Hangenberg Shale, HSS = Hangenberg Sandstone, LAS = Lower Alum Shale (= Kahlenberg Formation).

Sequence stratigraphy: LST = Lowstand System Tract, TST = Transgressive System Tract, HST = Highstand System Tract, FSST = Falling Stage System Tract.

Conodont genera/subgenera: Bi. = Bispathodus, Br. = Branmehla, Eo. = Eosiphonodella, Neo. = Neopolygnathus, Pa. = Palmatolepis, Po. = Polygnathus, Pr. = Protognathodus, Ps. = Pseudopolygnathus, S. = Siphonodella, Sc. = Scaliognathus.

Ammonoid genera/subgenera: Ac. = Acutimitoceras, B. = Balvia, C. = Cymaclymenia, Cost. = Costimitoceras, Cyrt. = Cyrtoclymenia, Eff. = Effenbergia, Eoc. = Eocanites, Epi. = Epiwocklumeria, F. = Finiclymenia, G. = Gattendorfia, Gl. = Globimitoceras, H. = Hasselbachia, K. = Kalloclymenia, Kamp. = Kamptoclymenia, Kaz. = Kazakhstania, Ken. = Kenseyoceras, Kos. = Kosmoclymenia, L. = Linguaclymenia, Liss. = Lissoclymenia, M. = Muessenbiaergia, May. = Mayneoceras, Mim. = Mimimitoceras, N. = Nicimitoceras, P. = Parawocklumeria, Pap. = Paprothites, Parag. = Paragattendorfia, Post. = Postclymenia, Pseud. = Pseudarietites, R. = Rectimitoceras, Sph. = Sphenoclymenia, St. = Stockumites, Str. = Streeliceras, Tria. = Triaclymenia, V. = Voehringerites, W. = Wocklumeria, Wey. = Weyerella.

SMNS = Staatliches Museum für Naturkunde Stuttgart (figured conodonts). All ammonoids, collection numbers B6C.54.1 to B6C.54.11, are deposited in the Geomuseum of the WWU at Münster.

Conodont biostratigraphy (Fig. 1)

The DCB conodont stratigraphy has been reviewed by Becker et al. (2016a), with subsequent nomenclatorical changes by Spalletta et al. (2017) and with a discussion in Söte et al. (2017). The pelagic facies zonation of the Sauerland cannot be applied to the shallow-water limestones of the Aachen and Velbert regions, which are, unfortunately, mostly very poor in conodonts. The zone definitions and terminology used here follow, with one exception at the main Hangenberg Extinction, the FADs of name-giving index species. The upper boundaries of zones/subzones are automatically defined by the base of the next higher zone/subzone. Besides the defining index species, there are other marker species, which have their FADs within given zones, but not necessarily precisely at the same level as the index species. For the literature of given reference beds, see the individual section descriptions. Examples of marker conodonts are given in Fig. 2.

Fig. 2
figure2

Some lower Tournaisian conodonts from the Rhenish Massif (northern Sauerland); all kept in the Staatliches Museum für Naturkunde Stuttgart (SMNS); scale bars = 0.2 mm. a Protognathodus cf. meischneri, specimen with narrow platform, Hangenberg, Bed 8, ?Siphonodella (Eosiphonodella) bransoni Zone, SMNS 70394/1; b–d Pr. collinsoni, Hangenberg, Bed 8, SMNS 70394/2; e–g Protognathodus sp., three specimens with atypical ornament transitional between Pr. kockeli and Pr. kuehni, Oberrhödinghausen Railway Cut (ORC), Bed 4b, lower part of S. (S.) duplicata Zone, SMNS 70394/3-5; h Pr. kockeli, transitional towards Pr. kuehni, ORC, Bed 6b, S. (Eo.) sulcata s.l./Pr. kuehni Zone, SMNS 70393/1-9 (Kaiser et al. 2017, fig. 10.9); i Pr. kuehni, Oese, Bed 4b, basal S. (Eo.) sulcata s.l./Pr. kuehni Zone, SMNS 70393/1-14 (Kaiser et al. 2017, fig. 10.14); j, k S. (Eo.) sulcata s.l., anterior platform with a slight trend towards S. (Eo.) bransoni, Drewer, Bed 12, S. (Eo.) sulcata s.l./Pr. kuehni Zone, SMNS 70394/6-7; l S. (Eo.) bransoni, ORC, Bed 5b, S. (Eo.) bransoni Zone, SMNS 70393/1-2 (Kaiser et al. 2017, fig. 10.2); m, n S. (S.) duplicata, ORC, Beds 4b (SMNS 70394/8) and 4a (SMNS 70391/1-3, Kaiser et al. 2017, fig. 10.3), S. (S.) duplicata Zone; o S. (S.) carinthiaca, Oese, Kaiser-Bed 21 = Bed Q = Bed 31, upper part of S. (S.) mehli Zone, SMNS 70393/1-11; p–r S. (S.) belkai M1, ORC Beds 3c2 (SMNS 70393/1-19, Kaiser et al. 2017, fig. 12.2, upper S. (S.) mehli Zone), ORC Bed 2b (SMNS 70393/1-8, Kaiser et al. 2017, fig. 12.1), S. (S.) sandbergi Zone, and ORC 2a (SMNS 70393/1-21, Kaiser et al. 2017, fig. 12.7, S. (S.) sandbergi Zone with S. (S.) quadruplicata); s S. (S.) lobata M2, ORC, Bed 3c2, upper S. (S.) mehli Zone, SMNS 70393/1-6 (Kaiser et al. 2017, fig. 10.6); t S. (S.) quadruplicata, morphotype with short, secondary rostral ridge only on the inner side, ORC, Bed 1b, top S. (S.) sandbergi Subzone, SMNS 70393/1-4 (Kaiser et al. 2017, fig. 10.4); u Pseudopolygnathus triangulus triangulus, ORC, Bed 2b, S. (S.) sandbergi Subzone, SMNS 70393/1-7 (Kaiser et al. 2017, fig. 10.8).

Bispathodus ultimus ultimus Zone (Becker et al. 2016a; Hartenfels and Becker 2016)

Synonyms: Lower part of Middle costatus Zone of Ziegler (1962) and Klapper and Ziegler (1979), Upper expansa Zone of Ziegler and Sandberg (1984b), lower part of Bi. ultimus Zone of Corradini et al. (2016).

Reference sections: Hasselbachtal (Beds -20S to 17S), Oese (Nowak-Beds 180b–186b), Oberrödinghausen (Schindewolf-Beds 23–18), Dasberg (Beds 0a-b), Reigern Quarry (Beds 5–22, Söte et al. 2017), Müssenberg (Beds 85–56), Effenberg (Bed 19 and higher), Eulenspiegel (Beds 5–10).

Other marker species: Palmatolepis gracilis gonioclymeniae, Ps. marburgensis trigonicus, Br. suprema.

Discussion: Since Bi. ultimus includes three subspecies with different stratigraphic ranges, the generalised Bi. ultimus Zone of Corradini et al. (2016) and Spalletta et al. (2017) had to be refined. It is important to note that their Bi. ultimus Zone embraced also a much longer time interval, until the base of the Pr. kockeli Zone (Becker et al. 2016a; Söte et al. 2017).

In the Rio Boreado section of the Carnic Alps, Bi. ultimus ultimus, Pa. gracilis gonioclymeniae, and Ps. marburgensis trigonicus enter synchronously (Kaiser et al. 2009). In other Carnic Alps sections and in the Rhenish Massif, the situation is much more complex. Pseudopolygnathus marburgensis trigonicus seems to enter first (base of Wocklum Limestone at Oberrödinghausen, Schindewolf-Bed 23, Bed 181b of Sacher 2016; Sample 11 of Eickhoff 1973), followed by Pa. gracilis gonioclymeniae and Br. suprema at the level of “Sphenoclymenia” cf. brevispina (Oberrödinghausen, Schindewolf-Bed 22, Kürschner et al. 1993; Bed 185b of Sacher 2016), and then by the name-giving zonal species (Müssenberg, Bed 80, Luppold et al. 1994; Oberrödinghausen, Schindewolf-Bed 20 = Bed 191b of Sacher 2016). It is well possible that more detailed sampling will change this picture. Currently, it is not clear whether the Rio Boreado or Rhenish patterns represent better the FADs of the three marker species.

The oldest Rhenish Pr. meischneri, which is the oldest member of Protognathodus, occurs at Oberrödinghausen in Bed 20 (Kürschner et al. 1993), slightly below the first Kalloclymenia. The taxon is much too rare in the Wocklum Limestone to have biostratigraphical significance. As outlined by Tragelehn (2010), Becker et al. (2013), and Söte et al. (2017), there are early relatives of Siphonodella, which represent two different genera. These “siphonodelloids” have Polygnathus-type upper platforms, for example as in Po. inornatus and Po. symmetricus, but non-polygnathid, extended basal cavities. The group requires detailed taxonomic treatment (see Tragelehn 2010; Becker et al. 2013). Both the Po. inornatus-symmetricus Group (see Corradini et al. 2016) and the “siphonodelloids” enter above the base of the Bi. ultimus ultimus Zone and specific forms may enable a future subdivision.

Siphonodella (Eosiphonodella) praesulcata s.l. Zone (Sandberg et al. 1978)

Synonyms: Lower praesulcata and basal Middle praesulcata Zones (below main Hangenberg Extinction) of Ziegler and Sandberg (1984a), upper part of extended Bi. ultimus Zone, but below the main Hangenberg Extinction, of Corradini et al. (2016).

Reference sections: Hasselbachtal (Beds 18S–114N), Oese (Nowak-Beds 187b–228a), Oberrödinghausen (Schindewolf-Beds 17–1, Kürschner et al. 1993), Wocklum (Beds -3b to −1b), Reigern Quarry (Beds 24–39, Söte et al. 2017), Müssenberg (Beds 55–4, Luppold et al. 1994), Eulenspiegel (Beds 11–15).

Discussion: Kaiser and Corradini (2011) showed the vague distinction between S. (Eo.) praesulcata and sulcata and the rather subjective past identifications of both taxa by different authors. The holotype of S. (Eo.) praesulcata comes in the Lick Creek type section of Montana from a level above Hangenberg Shale/Sandstone equivalents (= Units 4 and lower 5 of the Middle Sappington Formation, LN Zone, Di Pasquo et al. 2016), therefore from the Upper Crisis Interval (oolites at the top of Unit 5; Rice et al. 2017). As noted by Becker et al. (2016a), the FOD of any S. (Eosiphonodella) is currently used within the Wocklum Limestone to recognise the base of the S. (Eo.) praesulcata Zone in a wide sense (s.l.). This vagueness, however, does not necessarily require that the zone has to be abandoned, as proposed by Corradini et al. (2016). Kaiser et al. (2009) showed that it can be recognised in all sections that they studied in the Carnic Alps, Graz Palaeozoic, and the Pyrenees. Söte et al. (2017) documented that early S. (Eosiphonodella) can easily be found in Wocklum Limestone successions that are not very rich in conodonts (Reigern Quarry, Hachen). The taxonomy of pre-Crisis siphonodellids requires an intensive revision (e.g. Tragelehn 2010; Becker et al. 2013). Such a re-assessment will eventually lead to a refined zone defined by the FAD of the oldest S. (Eosiphonodella) species.

Subdivision: In the Müssenberg type section, Bi. muessenbergensis appears high in the S. (Eo.) praesulcata Zone (Bed 18, Luppold et al. 1994), at the level of the May. nucleus Subzone (UD VI-C3). This may provide a correlation level within the poorly calcareous “Wocklum Beds” of Stockum (Bed 172, Clausen et al. 1994). The oldest known Pr. collinsoni of the Rhenish Massif was listed together with various pre-Crisis palmatolepids, bispathodids, and Ps. marburgensis trigonicus from Seiler, Section I (Sample 1, Clausen et al. 1989a). This corresponds to an occurrence at the top of the S. (Eo.) praesulcata Zone at Grüne Schneid in the Carnic Alps (e.g. Kaiser et al. 2006; Corradini et al. 2017; Schönlaub 2018). Unfortunately, the species is too rare to be used as a zonal index form.

Bispathodus costatus-Protognathodus kockeli Interregnum (ckI, Kaiser et al. 2009)

Synonyms: Main part (above the noted conodont extinction) of the Middle praesulcata Zone sensu Ziegler and Sandberg (1984a).

Reference sections: Drewer (Beds 94–97); conodont-free Hangenberg Black Shale to Hangenberg Sandstone of other sections.

Discussion: Since the LOD of Pa. gracilis gonioclymeniae varies widely between sections, and even between different sampling campaigns of the same section, Kaiser et al. (2009) discarded the Middle praesulcata Zone and replaced it by the ckI, which was defined by the synchronous LOD of many taxa, such as Bi. costatus, Bi. ultimus ultimus, Ps. marburgensis trigonicus, Pa. gracilis gracilis, Pa. gracilis expansa, and Pa. gracilis sigmoidalis. Whilst these do not re-occur in the Upper and post-Crisis Intervals of calm pelagic carbonate platform settings (Kaiser et al. 2009), reworking and downslope transport at seamounts, or stratigraphic leak due to the bioturbation of extremely condensed successions, may lead to post-crisis occurrences, always in very low numbers, including various Rhenish sections. Their reworked nature has been questioned by several authors but the assumption of a survival without recovery and without a new spread into the easily accessible, stable platform settings is more unlikely.

In the Rhenish Massif, the ckI is mostly represented by siliciclastics that have not yielded any conodonts so far. Therefore, the regional ckI conodont record is very poor, with the exception of some limestone nodules from near its top at Drewer (Bed 97, Korn et al. 1994b). They yielded an assemblage with Pr. meischneri, Pr. collinsoni, and Neo. communis communis, which are common in ckI faunas of many other regions (see compilation in Becker et al. 2016a, p. 363). Since there are no newcomers in such faunas on a global scale, it is currently not possible to replace the ckI by a FAD-based zone.

Several attempts to retrieve conodonts from weathered Hangenberg Black Shale failed. So far, no conodonts have been observed on black shale bedding surfaces. It is theoretically possible that some victim taxa survived into the conodont-poor Lower Crisis Interval, similar as postclymeniids did among the ammonoids (see Corradini and Spalletta 2018).

Protognathodus kockeli Zone (Kaiser et al. 2009)

Synonyms: Upper praesulcata Zone of Ziegler and Sandberg (1984a), lower part of extended Pr. kockeli Zone in Corradini et al. (2016).

Reference sections: Neu-Moresnet (Reissner 1990), Oese (Bed A, Kaiser-Beds 3–4a, Korn-Beds 1–3), Apricke (Beds 39–37), Effenberg (3 cm calcareous shale with Guerichia to ca. Bed 18c), Hangenberg (Sample I of Luppold et al. 1994), Drewer (Beds 100 and 1), Wocklum (Beds ?3–5), Stockum (Beds 108–105), Eulenspiegel (Bed 21), Scharfenberg (Beds 1–3).

Other marker species: Polygathus purus subplanus (e.g. Drewer, Bed 1), Po. purus purus (Apricke, Bed 1H; Wocklum, Bed 4b), Neo. communis dentatus (Stockum, Bed 105). The type Stockum Limestone (Bed 103, upper part of Pr. kockeli Zone) yielded taxa that are not known from other localities, such as Po. marginvolutus, Neo. communis cf. carina, Ps. nodomarginatus, and Ps. cf. fusiformis (Clausen et al. 1994). A post-Crisis spread of pseudopolygnathids is more characteristic for the basal Hangenberg Limestone of other sections (see Scharfenberg).

Discussion: The precise use of the zone for a future DCB GSSP definition is hampered by a wide and variable definition of the species, which is based on intraspecific variability and rapid evolution of Protognathodus in the early recovery phase of the global Hangenberg Crisis. The types of Pr. kockeli come from the Wocklum or Borkewehr section, which is currently under re-study (Becker et al. 2016a; Becker and Hartenfels 2017 Hartenfels et al. 2017a, b; Hartenfels and Becker 2019). The holotype and figured paratypes of Bischoff (1957) represent advanced forms with either two rows of nodes on each platform side or incipient second rows (consisting of two nodes only) on one or both sides. In the first limestones above the Hangenberg Sandstone, there are much simpler forms, partly with only one row of nodes on one side and with at least three nodes defining a row. “Double-rowed” forms sensu Kaiser et al. (2019) possess a row of nodes on each platform side. Intermediates from Pr. collinsoni display at least on one side two nodes that are arranged in parallel to the carina. Complexly ornamented collinsoni variants possess many randomly distributed nodes. There are also Pr. kockeli morphotypes that are intermediate towards Pr. kuehni, (Figs 2e–h), which is characterised by transverse ridges. The total Protognathodus variability of the Stockum Limestone is even higher and includes aberrant morphotypes (e.g. specimens identified as Pr. praedelicatus, Pr. cordiformis, Protognathodus sp. A and B in Luppold et al. 1994). Kaiser et al. (2019) showed that platform shape (e.g. asymmetry) and blade curvature are less useful to define specific Protognathodus morphotypes but these features require further evaluations (Kaiser and Hubmann, this vol.). The precise succession of morphotypes and their ontogeny and variability have to be worked out before protognathodids can be used as a DCB GSSP criterion.

Polygnathus purus purus enters at Wocklum in the second bed of the Pr. kockeli Zone (Bed 4b, Hartenfels et al. 2017a). However, Kaiser (2009) noted a much earlier occurrence in the Montagne Noire, from Bed 70 (lower ckI) of the current DCB GSSP at La Serre, which is the bed just above the supposed HBS equivalent (Bed 69; see Feist et al. 2020). Supposed pre-Crisis occurrences reported by Corradini et al. (2003) have not been illustrated. Close relatives of Po. purus purus characterised by a more anterior position of the basal pit were described from the upper ckI of southern Morocco (Becker et al. 2013) and identified as Po. cf. purus purus. They suggest that it is possible to distinguish very early and typical forms of the subspecies.

Siphonodella (Eosiphonodella) sulcata s.l./Protognathodus kuehni Zone (Kaiser et al. 2009)

Synonyms: Higher part of the extended Pr. kockeli Zone in the scheme of Corradini et al. (2016).

Reference sections: Hasselbachtal (Beds 84N–81N), Oese (Beds B–E = Kaiser-Beds 4b–8 = Korn-Beds 4–11), Apricke (Beds 6H-10H = 36–35), Oberrödinghausen (Beds 6A–5c, Voges-Samples 1–3), Effenberg (ca. Beds 18d-l), Hangenberg (Sample II of Luppold et al. 1994), Müssenberg (Beds 3a–3B), Stockum (Beds 100–97, especially Unit Alb-C-c, Sample 330 of Alberti et al. 1974), Drewer (Beds 3–4), Eulenspiegel (Bed 22), Scharfenberg (Beds 4–5).

Other index species: At Stockum, Bed 100 yielded Ps. fusiformis (Clausen et al. 1994). The alternative shallow-water siphonodellids of South China (e.g. S. (Eo.) homosimplex, S. (Eo.) semichatovae) have not yet been found in Rhenish sections. The same applies to Clydagnathus-Patrognathus faunas that appear in the basal Tournaisian of Russian and Chinese sections (e.g. Becker et al. 2016a; Zhuravlev et al. 2018).

Discussion: Kaiser and Corradini (2011) documented the currently subjective identification of S. (Eo.) sulcata in many papers. Many specimens do not conform to the type North American lost specimen, which came from the basal Tournaisian Henryville Bed within the Ellsworth Member of the New Albany Shale (Evans et al. 2013). Until further revision, curved and ribbed basal Carboniferous siphonodellids are referred to as S. (Eo.) sulcata s.l. Following Kaiser and Corradini (2011), it is their Morphotype 5 that has the best potential to define a refined S. (Eo.) sulcata Zone. A joint S. (Eo.) sulcata s.l./Pr. kuehni occurrence in the top Stockum Limestone at Seiler, Section I (Bed 5), resulted in a first close alignment of both FADs (Clausen et al. 1989a). Based on direct co-occurrences in the Graz Palaeozoic and Carnic Alps, Kaiser et al. (2019) confirmed the usefulness of (typical) Pr. kuehni as an alternative index species for the S. (Eo.) sulcata (s.l.) Zone. This is especially important for the majority of sections, where siphonodellids are absent in the Upper Crisis Interval (Stockum Limestone and equivalents, see compilation of Kaiser et al. 2015, tab. 5). It results in a combined S. (Eo.) sulcata s.l./Pr. kuehni Zone that ranges from Upper Crisis Interval III into the basal post-crisis time (basal Hangenberg Limestone). However, revisions of Protognathodus taxonomy, especially of the complex Pr. kockeli-kuehni transition (see Kaiser et al. 2019), have to consider the fact that the types of Pr. kuehni are not from the S. (Eo.) sulcata s.l./Pr. kuehni Zone, but from the younger S. (S.) duplicata Zone at Seiler, Trench 2.

Siphonodella (Eosiphonodella) bransoni Zone (Ji 1985)

Synonyms: Lower duplicata Zone of Sandberg et al. (1978).

Reference sections: Hasselbachtal (Beds 72H–70H), Oese (Beds F–I = Kaiser-Beds 9–12 = Korn-Beds 12–17), Apricke (Beds 13H/14H = 33), Oberrödinghausen (Bed 5b and Kürschner-Bed 4), Seiler, Section II (Bed 10), Drewer (Bed 5), ?Stockum (Unit Alb-C-e = Bed 95), Scharfenberg (Bed 6), Eulenspiegel (Bed 23).

Discussion: Ji (1985) re-named S. duplicata M1 as S. (Eo.) bransoni. As discussed below, it is possible that Ps. triangulus inaequalis enters within the S. (Eo.) bransoni Zone.

Siphonodella (Siphonodella) duplicata Zone (Ji 1985)

Synonyms: Possibly the triangulus inaequalis Zone of Voges (1960).

Reference sections: Hasselbachtal (Beds 69H–65H), Oese (Kaiser-Bed 13), Oberrödinghausen (Beds 4a–4b, Kaiser et al. 2017; Kürschner-Beds 5–6), Seiler, Section 0 (Bed 3), Section II (Beds 11–12), Section III (Beds 4–6), Stockum (Unit Alb-D, Samples 315–316), Scharfenberg (Bed 7).

Other marker species: Possibly Pseudopolygnathus triangulus inaequalis (e.g. Seiler, Section 0, Bed 3, Hasselbachtal, Bed 69H, Oberrödinghausen, Bed 4 = Sample 5, Voges 1959), S. (S.) lobata M2 (Oberrödinghausen, Bed 4 = Sample 5, Voges 1959).

Discussion: The lowest range of Ps. triangulus inaequalis requires further data. Without specific information, Ziegler (1971) placed the base of the “triangulus inaequalis Zone” at Oese between Beds F and G, which is well below the locally oldest S. (S.) duplicata in Bed J. The entry of early relatives of S. (Eo.) isosticha (e.g. at Hasselbachtal from Bed 65H on) requires also further work.

Siphonodella (S.) mehli Zone (nom. nov.)

Synonyms: Upper duplicata Zone of Sandberg et al. (1978), jii Zone of Becker et al. (2016a), triangula triangula Zone of Voges (1959, 1960).

Reference sections: Hasselbachtal (Beds 63H–45H), Seiler, Section 0 (Bed 4 with S. (S.) mehli, S. (S.) cooperi, and S. (S.) carinthiaca, Beds 5–6), Section II (Bed 13 with S. (S.) mehli and S. (S.) carinthiaca, Beds 14–16), Section III (Bed 6 with Ps. triangulus triangulus, Bed 7 with S. (S.) mehli, S. (S.) carinthiaca, and S. (S.) cooperi; Clausen et al. 1989a), Oese (?Kaiser-Bed 14 with S. (S.) duplicata and S. (S.) cf. wilberti, Kaiser-Bed 17 with S. (S.) carinthiaca and S. (S.) belkai M1, Kaiser-Bed 21 with S. (S.) carinthiaca, S. (S.) cf. wilberti, and S. (S.) lobata M2, Kaiser-Bed 22 with S. (S.) obsoleta), Oberrödinghausen (?Bed 3e, Beds 3d–3b = Ziegler-Beds ?9–13 with S. (S.) belkai M2, S. (S.) cf. wilberti, S. (S.) lobata M2, and S. (S.) obsoleta; Korn and Weyer 2003; Kaiser 2005; Kaiser et al. 2017: Kürschner-Beds 8–12), Müssenberg (Bed 0 with S. (S.) carinthiaca and Ps. triangulus triangulus), Stockum (Unit Alb-D, Sample 918), Drewer (Beds 6/7 with S. (S.) carinthiaca and S. (S.) cooperi, Beds 8/9 with S. (S.) mehli and “S. duplicata sensu Hass” (= S. (S.) cf. wilberti), Scharfenberg (?Beds 8–9 with S. (S.) cf. wilberti, Beds 10–11 with S. (S.) mehli and S. (S.) carinthiaca), Eulenspiegel (Bed 24 with S. (S.) mehli, S. (S.) carinthiaca, and S. (S.) cf. wilberti).

Other marker species: S. (S.) carinthiaca (Hasselbachtal, Beds 59H–47H; Seiler, Section 0/Beds 4–5, Section II, Beds 13–14, Clausen et al. 1989a; Oese, Bed 21, Kaiser et al. 2017; new records from Borkewehr), S. (S.) cooperi (= M2; Hasselbachtal, Bed 65H; Seiler, Section 0/Bed 4, Clausen et al. 1989a), Ps. triangulus triangulus (Hasselbachtal, Beds 49H–47H), Drewer, Beds 6–7; Seiler, Section 0, Beds 4–5).

Discussion: Sandberg et al. (1978) based their Upper duplicata Zone on the FAD of S. cooperi M1, which was re-named by Ji (1985) as S. (S.) mehli. Ji (1985), by contrast, used the FAD of S. duplicata sensu Hass, which he re-named as S. (S.) hassi, to define a supposedly corresponding hassi Zone. Becker et al. (2016a) recognised that S. (S.) hassi Ji 1985 is an invalid junior homonym of S. cooperi hassi Thompson and Fellows 1970, and, consequently, re-named S. duplicata sensu Hass as S. (S.) jii, with two originals of S. duplicata var. A of Hass (1959) as type specimens. The adult USNM 115140, the original of Hass (1959, pl. 49, fig. 18), is here selected as the lectotype. The species re-naming resulted in a name change from hassi Zone to jii Zone. Zhuravlev and Plotitsyn (2018) re-illustrated the types of S. (S.) jii and showed the presence of incipient second rostral ridges, at least on the inner anterior platform. In this respect, the morphology of the jii lectotype is less advanced than in typical adult S. (S.) quadruplicata (see Zhuravlev and Plotitsyn 2018: fig. 3). The specimen can be regarded as an early morphotype (M2) of S. (S.) quadruplicata. The second, smaller specimen (Hass 1959, pl. 49, fig. 17) fits well into an ontogenetic series of S. (S.) quadruplicata from the Polar Urals. Chinese specimens of “S. (S.) hassi” do not display incipient secondary rostra, apparently throughout ontogeny. They may be assigned to S. (S.) wilberti Bardasheva Bardashev, Weddige and Ziegler, 2004 described from the middle Tournaisian of Tadzhikistan. The wilberti holotype is characterised by a peculiar, undulating and serrate outer platform corner, which could be a pathological feature. Until the variability of S. (S.) wilberti is better known, we suggest to name specimens of “S. (S.) hassi sensu Ji 1985” as S. (S.) cf. wilberti. Although representatives from the Rhenish Massif have never been illustrated, we preliminary extend this assignment to previously reported Rhenish “S. duplicata sensu Hass”. We are aware that some of these specimens may be identical with S. (S.) jii sensu its lectotype (= S. (S.) quadruplicata M2). This has to be clarified by the revision of specimens and the study and illustration of additional faunas.

In order to avoid these taxonomic complications, the jii Zone of Becker et al. (2016a) is replaced by the re-named S. (S.) mehli Zone, returning to the original definition of the Upper duplicata Zone by Sandberg et al. (1978). However, it is unfortunate that S. (S.) mehli (= cooperi M1) is relatively rare in several sections of the Rhenish Massif.

Subdivision: Sandberg et al. (1978) suggested that S. (S.) carinthiaca and S. (S.) cooperi s. str. (= Morph 2) enter later than S. (S.) mehli (= S. cooperi M1). Published faunas from Rhenish sections do not provide any support. As explained below, the FAD of S. (S.) quadruplicata occurs in several sections in the S. (S.) mehli Zone or even before (e.g. Seiler Trench 2, Bed 14, Koch et al. 1970), well before the entry of S. (S.) sandbergi or S. (S.) lobata. Currently, it is unclear whether all or only some of these records refer to the early M2 in the sense of the S. (S.) jii lectotype.

Sandberg et al. (1978) showed that the FAD of S. (S.) obsoleta lies near the top of the Upper duplicata Zone (e.g. Oese, Kaiser-Bed 22b = R; Seiler sections, compare range in Ji 1985). The species occurs at Oberrödinghausen well below the base of the sandbergi Zone (Bed 3d2 = Voges 1959, Sample 6) and jointly with the first S. (S.) belkai M2 (Kaiser et al. 2017). The FADs of both taxa mark in the Rhenish Massif a position in higher parts of the S. (S.) mehli Zone but currently we refrain from proposing a new subzone.

Since Voges (1959), various authors correlated the triangulus triangulus Zone with a high level in the Hangenberg Limestone (e.g. Ziegler 1971). However, there is evidence from several sections (Drewer, Seiler sections) that the index species may enter much lower, around the base of the S. (S.) mehli Zone. For example, Koch et al. (1970) recorded Ps. triangulus triangulus at Seiler Trench 2 from Bed 13, below the FAD of S. (S.) obsoleta. Ziegler (1971) marked at Oese the base of the triangulus triangulus Zone at the base of Bed M, within the range of Paprothites (Korn and Weyer 2003). A possibly even earlier record was listed by Luppold et al. (1994) from Müssenberg (Bed 1). Eickhoff (1973) noted at Oberrödinghausen a joint entry of Ps. triangulus inaequalis and Ps. triangulus triangulus in his Sample 3, correlated with Sample 5 of Voges (1959), which is in the S. (S.) duplicata Zone. More precision of the Ps. triangulus ssp.-siphonodellid correlation is required.

Siphonodella (Siphonodella) sandbergi Zone (Sandberg et al. 1978)

Reference sections: Oberrödinghausen (Beds 2b–1a, Kaiser 2005; Kürschner-Sample 13), Stockum (Unit Alb-D, Samples 921, 919).

Other marker species: Siphonodella (Eo.) cf. isosticha (Oberrödinghausen, Bed 1b, Ziegler 1971; Seiler, Section 0, Bed 10, Clausen et al. 1989a).

Discussion: Siphonodella (S.) sandbergi is rather rare in the Rhenish Massif and, therefore, its zone is difficult to recognise apart from Oberrödinghausen and Stockum. In several sections, S. (S.) quadruplicata, possibly M2, was reported to enter jointly with “S. duplicata sensu Hass” (= S. (S.) cf. wilberti; e.g. Drewer, Bed 9), below (Seiler, Trench 2, Bed 14) or with the first S. (S.) obsoleta (Seiler, Section III, Bed 8, Section 0, Bed 6), or with S. (S.) cooperi (M2, Seiler, Section II, Beds 15–16), in all cases without any evidence for S. (S.) sandbergi (compare early ?quadruplicata records at Stockum, Groos-Uffenorde and Uffenorde 1974). This questions the quadruplicata Zone of Ji (1985), which he established for an upper subdivision of the sandbergi Zone. Siphonodella (S.) quadruplicata occurs commonly in higher parts of the S. (S.) sandbergi Zone of some sections (e.g. at Scharfenberg, Beds 13–14, Clausen et al. 1989a, and at Oberrödinghausen, Kaiser 2005; Kaiser et al. 2017). It may be possible to separate typical/late (M1) and early morphotypes (M2) but this requires a better documentation. Currently we hesitate to recognise a S. (S.) quadruplicata Zone (better subzone) in the top Hangenberg Limestone of the Rhenish Massif. The S. (S.) sandbergi/quadruplicata range relationships are not much clearer in the Montagne Noire (Kaiser et al. 2009; Feist et al. 2020: with S. (S.) quadruplicata entering before S. (S.) sandbergi at Col de Puech de la Suque) or in the Carnic Alps (e.g. Kronhofgraben, Kaiser et al. 2006). The S. (S.) quadruplicata Zone also has not been recognised in the recent review of Chinese Carboniferous conodont zones by Hu et al. (2019).

Subdivision: Sandberg et al. (1978) suggested that the entry of S. (S.) lobata could be used to separate an upper subzone. This is supported by records from the top Hangenberg Limestone of Apricke (Bed 34H = 16), Oberrödinghausen (Bed 1a = Voges 1959, Sample 11), Seiler (all sections), Drewer (Bed 12), Stockum (Unit Alb-D, Sample 353), and Scharfenberg (Beds 12–14, Clausen et al. 1989a). Voges (1959, pl. 35, figs. 35, 36, 38) illustrated typical specimens that share with the North American holotype an anterior direction of the side lobe marked by a secondary carina. This form is here called Morph 1. Other specimens (e.g. Voges 1959, pl. 35, fig. 39) and especially older representatives (Ji et al. 1989, pl. 14, figs. 3–4, basal sandbergi Zone; Kaiser et al. 2017, figs. 10.6 and 10.13, “jii Zone”) have a more incipient platform lobe directed to the side, which lacks on the oral surface a secondary carina. These are assigned to our new Morph 2. Only S. (S.) lobata M1 indicates the upper S. (S.) sandbergi Zone or S. (S.) lobata M1 Subzone. The base of the S. (S.) crenulata Zone forms the top of the new subzone. For associated siphonodellids and other conodonts, see the range charts in Sandberg et al. (1978), Clausen et al. (1989a), and Ji (1985).

Ammonoid biostratigraphy (Fig. 1)

The DCB ammonoid biostratigraphy has been reviewed by Becker et al. (2016a), who emphasised parallel zonations based on successive members of the Prionoceratidae, Kosmoclymeniidae, other clymeniid groups, and, in the lower Tournaisian, early prolecanitids. A different approach was followed by Klein and Korn (2016), who used three quantitative methods (unitary associations, ranking and scaling, constrained optimisation) to correlate Rhenish records (reference sections Müssenberg 1 for the upper/uppermost Famennian, Oberrödinghausen Railway Cut for the lower Tournaisian) and to establish composite ranges. These, however, differ from each other and the correlation obviously did not consider other stratigraphic markers, such as conodonts and metabentonites. The Rhenish Slate Mountains yielded on a global scale the most detailed DCB ammonoid record. Several ammonoid subzones are based on the detailed classical studies by Schindewolf (1937) and Vöhringer (1960). Subsequent studies and revisions added many precise data and taxa (e.g. Korn 1981a, b, 1984, 1988a, 1988b, 1991, 1992a, b, 1993, 1994, 2000; Becker 1988, 1996, 2000; Clausen et al. 1989a, b; Korn and Luppold 1987; Luppold et al. 1994; Korn et al. 1994b; Korn and Weyer 2003; Korn and Vöhringer 2004; Ebbighausen and Korn 2007; Becker et al. 2016a) but in general supported the originally established faunal sequence. The current knowledge of Rhenish DCB ammonoid zones/subzones, with all units (apart from the Post. evoluta Zone) named after the FAD of its index species, is from base to top (for reference section literature, see section descriptions):

Linguaclymenia similis Zone (Becker et al. 2002, UD VI-A1)

Synonyms: Muessenbiaergia sublaevis Zone (Korn 2000).

Other marker species: Muessenbiaergia sublaevis (Müssenberg, Bed 90; Dasberg, Bed L), “Mim.liratum (Müssenberg, Bed 90), “Mim.geminum (Hasselbachtal, Bed 1S; Dasberg, Bed K), Kos. undulata (Müssenberg, Bed 90), Rodachia dorsocostata (Müssenberg, Bed 90), C. semistriata (Effenberg, Figs. 5i–j), Cyrto. plicata (Müssenberg, Bed 90), Cyrto. lateseptata (Hasselbachtal, Bed 1, ?= Cyrto. campanulata), “Sph.brevispina (cf. Oberrödinghausen, Schindewolf-Bed 22; Effenberg, Bed 17), “Sph.erinacea (Dasberg, Bed 0a = L), R. quadripartitum (Hasselbachtal, Bed 2).

Reference sections: Müssenberg (Beds 90–68), Hasselbachtal (3 m below Bed 0 to Bed 12), Oberrödinghausen (Schindewolf-Beds 23-ca. 19), Dasberg trench (Korn and Luppold 1987, base of Bed 0b; Clausen and Korn 2008, Beds L–J), Effenberg (kosmoclymeniid coquinas, Hartenfels et al. 2016).

Discussion: Schindewolf (1937) proposed to use the entry of Kalloclymenia (s.l., at his time including various sphenoclymeniids and Finiclymenia) to define the base of the Wocklum Beds and a Kalloclymenia-Wocklumeria-Stufe. However, in his type section in the Oberrödinghausen Railway Cut, bed-by-bed collecting started with Bed 23, from which he recorded “Oxyclymenia bisulcata”. At his time, such an identification referred to kosmoclymeniids with marked ventrolateral furrows, which included, among others, forms now assigned to Linguaclymenia, especially L. similis (see synonymy list in Korn and Price 1987). Therefore, it can be assumed that Schindewolf’s section began locally with the FOD of Linguaclymenia. The first “Kalloclymenia”, in fact “Sph.” cf. brevispina, commenced one bed higher, which led to the term K. subarmata-K. brevispina Zone. Korn and Luppold (1987) subdivided the zone and defined their “Lower subarmata Zone” by the entry of “Sph.brevispina, stimulated by new records of that species from Dasberg and Effenberg. However, in the subsequent review of “Sph.brevispina by Price and Korn (1989), the Dasberg specimens were re-assigned to a new species, “Sph.erinacea (see also Clausen and Korn 2008). This showed that several “sphenoclymeniids” enter in the basal Wocklum Beds. The phrase “Sphenoclymenia” refers to the distinction of moderately large forms with narrowly rounded venter from the poorly known, giant-sized, oxyconic-type species of the genus, Sph. maxima.

At Müssenberg (Korn 1993; Klein and Korn 2016), M. sublaevis and L. similis enter jointly in Bed 90. This was obviously the base for a re-definition of the Wocklum-Stufe by the FAD of M. sublaevis (Korn 2000), although “Sph.brevispina enters at Müssenberg five beds higher. Because kosmoclymeniids are more common than “sphenoclymeniids”, we accept Korn’s slight extension of the Wocklumeria-Stufe but give preference to L. similis as the main index species. It is very distinctive and more easily recognisable than M. sublaevis in poorly preserved faunas without shell, even as small fragment. In addition, its zone can be traced widely, for example to Morocco (Becker et al. 2002). A joint FAD of L. similis and M. sublaevis was also shown at Dasberg (Clausen and Korn 2008).

Subdivision: Hartenfels and Becker (2016) re-habilitated Kalloclymenia (s.str.) as a marker genus for the lower Wocklumian. It enters at Oberrödinghausen (Schindewolf-Bed 19: K. cf. uhligi), Müssenberg (Bed 78: K. subarmata), and Hasselbachtal (Bed 2: K. pessoides) well above the base of the L. similis Zone (compare ranges in Klein and Korn 2016). However, Korn and Luppold (1987) noted a Kalloclymenia sp. from the second bed of the Wocklum Limestone at Dasberg.

Muessenbiaergia galeata enters in higher parts of the zone (Dasberg, Bed K; Hasselbachtal, Bed 12, Becker 1996; see RASC plot of Klein and Korn 2016: fig. 11).

Conodont correlation: The entries of L. similis and M. sublaevis pre-date at Müssenberg the FODs of any of the three main marker conodonts for the Bi. ultimus ultimus Zone. “Sphenoclymeniabrevispina begins jointly with Ps. marburgensis trigonicus (Bed 85), K. subarmata (in Bed 78) slightly above the FODs of Bi. ultimus ultimus (= ziegleri ziegleri) and Pa. gracilis gonioclymeniae (Bed 80, Luppold et al. 1994). At Effenberg “Sph.brevispina occurs in Bed 17 below Pa. gracilis gonioclymeniae (Bed 19); the local first K. subarmata was recorded from well above it (Bed 23). In the Dasberg trench, K. subarmata was also found above (Bed 0b) the oldest Pa. gracilis gonioclymeniae (Bed 0a; Korn and Luppold 1987). At Oberrödinghausen, Bed 23 of the basal Wocklum Limestone yielded Ps. marburgensis trigonicus (Sacher 2016), Bed 22 with “Sph.” cf. brevispina produced Pa. gracilis gonioclymeniae and Br. suprema (Kürschner et al. 1993), and Bed 20, below the oldest Kalloclymenia (in Bed 19), Bi. ultimus ultimus.

The complete evidence is a mosaic from these different sections. It suggests that the base of the Bi. ultimus ultimus Zone, if defined by either of the three main markers, lies close to the base of the L. similis Zone. Bispathodus ultimus ultimus, the proposed index fossil for the definition of a formal uppermost Famennian substage, however, does not display consistent FODs in individual sections and partly very long delays. Its oldest regional occurrence post-dates the oldest “Sph.brevispina. This suggests that Bi. ultimus ultimus was ecologically sensitive in pelagic facies.

Muessenbiaergia bisulcata Zone (Korn 2000; UD VI-A2)

Synonyms: Upper subarmata Zone, lower part (Korn and Luppold 1987).

Reference sections: Müssenberg (Beds 67–39), Hasselbachtal (Beds 14–31), Effenberg (“Bed 93d” with M. parundulata), Reigern Quarry (ca. Beds 10b–21), Dasberg trenches (Beds I–G).

Other marker species: Muessenbiaergia parundulata (Müssenberg, Bed 67),C.barbarae (Oberrödinghausen, Schindewolf-Bed 16), “Cyrto.tetragona (Oberrödinghausen, Schindewolf-Bed 18).

Conodont correlation: Based on the Müssenberg section (Clausen et al. 1989b), the base of the M. bisulcata Zone (Bed 67) lies well below the FAD (Bed 55) of S. (Eosiphonodella).

Effenbergia lens Zone (UD VI-B)

Reference sections: Müssenberg (Beds 38–35), Hasselbachtal (Beds 32–43), Oese (within Becker-package 4, Nowak-Bed 210l), Oberrödinghausen (Schindewolf-Beds 15–11 with “Prionoceras n. sp. IV”), Reigern Quarry (?Beds 27–28, Price 1982).

Other marker species: The FODs of several species are known from middle (Mim. trizonatum, Oese, within Nowak-Bed 210, Dasberg, Bed E) to upper parts of the zone: Eff. minutula (Oese, Nowak-Bed 210j, Dasberg, Bed D), M. ademmeri (Dasberg Bed D), Kos. schindewolfi (Oberrödinghausen, Schindewolf-Bed 12; Dasberg, Bed D), C. cf. sudetica (Oberrödinghausen, Sacher-Bed 204b), Soliclymenia solarioides (Dasberg, Bed D), and Gl. glaucopis (Dasberg, Bed D; Oese, Nowak-Bed 210l).

Discussion: Already Korn (1992a) and Luppold et al. (1994) recognised the level of Eff. lens and Eff. minutula as an upper subdivision of their “Late K. subarmata Zone” but the zone was not formally named until Korn (2000). It can be followed to southern Morocco (Becker et al. 2002).

Conodont correlation: Based on the Müssenberg section (Clausen et al. 1989b), the base of the Eff. lens Zone (Bed 38) lies well above the FAD (Bed 55) of S. (Eosiphonodella). This is supported by less detailed data from Oese (Nowak 2008).

Parawocklumeria paprothae Zone and Subzone (Clausen et al. 1989a; UD VI-C1)

Synonyms: Kamptoclymenia endogona Zone (or Subzone; Schindewolf 1937).

Reference sections: Müssenberg (Beds 34–26), Hasselbach-tal (ca. Beds 44–63), Oberrödinghausen (Schindewolf-Beds 10–7), Dasberg (Beds B–A).

Other marker species: Parawocklumeria patens (Müssenberg, Bed 34; Dasberg, Bed B), P. distorta (Oberrödinghausen, Schindewolf-Bed 10; Dasberg, Bed A), Kamp. endogona (Müssenberg, Bed 34; Dasberg, Bed A), Kamp. trigona (Müssenberg, Bed 34; Dasberg, Bed A), Tria. triangularis (Oberrödinghausen, Schindewolf-Bed 10), M. ?xenostriata (Hasselbachtal, Beds 46–49, above the LOD of Eff. lens), Eff. falx (Müssenberg, Bed 34; Dasberg, Bed B), B. globularis (Müssenberg, Bed 34), Ken. rostratum (= biforme; Dasberg, Bed B).

Subdivision: Somewhat above the zonal base (e.g. Müssenberg, Bed 29; Dasberg, Bed A), the distinctive Liss. wocklumeri enters.

Discussion: It is a matter of personal preferences to separate this level as a full zone or as a lower subzone (applied here) of the longer interval characterised by Parawocklumeria faunas before the onset of Wocklumeria. Since Kamptogona tends to be rare, the more common P. paprothae (see Becker 2000) is given preference as the index taxon.

Conodont correlation: The P. paprothae Subzone lies entirely within the S. (Eo.) praesulcata s.l. Zone.

Parawocklumeria paradoxa Subzone (Schindewolf 1937, UD VI-C2)

Reference sections: Müssenberg (Beds 25–20), Hasselbachtal (Beds 64-ca. 83cN), Oese (Becker-package 2), ?Oberrödinghausen (parts of Schindewolf-Beds 7–6).

Other marker species:Mimimitoceraslentum (Müssen-berg, Bed 25, Klein and Korn 2016).

Conodont correlation: The P. paradoxa Subzone lies entirely within the S. (Eo.) praesulcata s.l. Zone.

Mayneoceras nucleus Subzone (Becker et al. 2002, UD VI-C3)

Reference sections: Müssenberg (Beds 19–14), Hasselbach-tal (Beds 84N–91N), Oese (Nowak-Beds 225b–226d), Oberrödinghausen (main Schindewolf-Bed 6).

Other marker species: Finiclymenia wocklumensis (Müssenberg, Bed 17; Oese, cf. Nowak-Bed 225b), Postglatziella carinata (Müssenberg, Bed 17), possibly May. sinuconstrictum (Oese, Figs. 5g–h).

Conodont correlation: The May. nucleus Subzone lies entirely within the S. (Eo.) praesulcata s.l. Zone.

Discussion: Successive FADs of P. paradoxa and May. nucleus were confirmed by quantitative analyses of Klein and Korn (2016). Contemporary faunas with Finiclymenia and May. nucleus occur also in North Africa (Becker et al. 2002: section Lambidia).

Wocklumeria denckmanni Zone and Subzone (Schindewolf 1937, UD VI-D1)

Reference sections: Hasselbachtal (Beds 92N–112N; Figs. 5c–d), Oese (Korn-Bed 2, Becker-package 1, Nowak-Beds 226e–227c), Apricke (Beds 3–2), Oberrödinghausen (Schindewolf-Beds 5–2), Wocklum (Bed 3), Müssenberg (Beds 13–ca. 6), Drewer (Beds 91b–c), Grimminghausen (Wocklumeria record of Weber 1934).

Other marker species: Wocklumeria sphaeroides (Drewer, Bed 91b, Becker et al. 2016b), C. nephroides (Bilstein, Korn 1981a). In siliciclastic facies, Post. evoluta occurs. Its type level is at the top of the subzone at Drewer but its full and possibly lower range is currently unknown in the neritic sections of the Bergisches Land.

Discussion: The morphometric study of Ebbighausen and Korn (2007) showed that Rhenish wocklumeriids differ from the W. sphaeroides type population of Thuringia. Therefore, the long disused name W. denckmanni was revived for the typical Sauerland representatives. However, sphaeroides-type specimens, without marked triangular stage and with early rotund whorls, do occur in the Rhenish Massif. Due to a high variability of relative whorl and umbilical width, W. aperta Schindewolf, 1937 and W. plana Schindewolf, 1937 were placed by Ebbighausen and Korn (2007) in synonymy of W. denckmanni. Both names can be used to characterise intraspecific morphotypes (e.g. Fig. 3a–d), which distributions in space and time need further considerations.

Fig. 3
figure3

Examples for DCB ammonoids from the eastern Rhenish Massif; scale bar = 5 mm. a, b Wocklumeria denckmanni, adult specimen, Drewer, Bed 93 (UD VI-D2), leg. 2019, lateral and ventral views, B6C.54.1, × 1.5; c, d W. denckmanni, rather compressed middle-sized specimen with triangular constrictions, Hasselbachtal, loose (UD VI-D), lateral and ventral views, B6C.54.2; × 1.7; e, f Parawocklumeria paradoxa, Hasselbachtal, Bed 103N (UD VI-D1), lateral and ventral views, B6C.54.3, × 1.7; g, h Mayneoceras sinuconstrictum, Oese, collected from debris (UD VI-C/D), first record for the Rhenish Massif, lateral and ventral views, B6C.54.4, × 3; i, j Cymaclymenia semistriata, Effenberg, loose (UD VI), lateral and ventral views, more compressed than C. cf. sudetica, B6C.54.5, × 1.5; k Postclymenia cf. evoluta, squashed, Oese, HBS, B6C.54.6, × 1; l, m Gattendorfia subinvoluta, specimen with rursiradiate constrictions (unlike the type material), Oberrödinghausen Railway Cut, Bed 5 (LC I-A3), lateral and ventral views, B6C.54.7, × 1.5; n, o Paragattendorfia cf. sphaeroides, new rather involute variant of the species with relatively high whorls, Oberrödinghausen Railway Cut, level unclear, lateral and adoral views, B6C.54.8, × 2; p, qG.costata, topotype, Oberrödinghausen Railway Cut, Bed 2 (lower LC I-D), lateral and ventral views showing the strongly concavoconvex cornament (unlike the ornament in typical gattendorfiids), B6C.54.9, × 1.5; r, s fragmentary Acutimitoceras (Streeliceras) heterolobatum, Drewer, collected from debris, lateral and ventral views showing typical sutures with short, slightly pouched ventral lobes, new local record, B6C.54.10, × 1

Conodont correlation: The W. denckmanni Subzone lies entirely within the S. (Eo.) praesulcata s.l. Zone.

Epiwocklumeria applanata Subzone (Schindewolf 1937, UD VI-C2)

Reference sections: Hasselbachtal (Beds 113aN–114N), Oberrödinghausen (Schindewolf-Bed 1), Drewer (Beds 93a–c, with the last W. denckmanni, Figs. 5a–b), Wocklum (ca. Beds –2 to –1).

Conodont correlation: The Epi. applanata Subzone lies at the top of the S. (Eo.) praesulcata s.l. Zone, within the former Upper costatus Zone sensu Ziegler (1962). It equals the basal part of the Middle praesulcata Zone sensu Ziegler and Sandberg (1984b).

Postclymenia evoluta Zone (Schindewolf 1937, UD VI-E)

Reference sections: Lintorf area (Diepenbrock Anticline, Paul 1938a), Cromford (Beds 22–23) and adjacent localities, Scharpenhaus (Beds 2–3, Paul 1939a, p. 676), Hefel (Bed 1), Riescheid, Am Haken Brickwork Quarry, Mirker Hain, ?B224 building site near Aprath (pyritic Bed 05/30, with Acutimitoceras sp. but without conodont record), Hasselbachtal (Bed 115N), Apricke (Bed 42), Oberrödinghausen (Sacher-Bed 225), Oese (Nowak-Bed 229; Fig. 3k), Drewer (Bed 94), Vingerhoets 93 Well (1716–1720 m).

Discussion: The zonal base is defined by the LAD of all ammonoid taxa (especially of Wocklumeria, Epiwocklumeria, Parawocklumeria, Finiclymenia, Lissoclymenia, Cyrtoclymenia, N. Gen. aff. Cyrtoclymenia (“Pricella homoeomorph”), the “Cyrto.tetragona Group, Mayneoceras, Kenseyoceras, Balvia, Sporadoceras, and Ebbighausenites) apart from Postclymenia, NOT by the Post. evoluta FAD (Becker 1988). The term P. evoluta Zone was chosen, because there is hardly any other ammonoid apart from postclymeniids in the HBS. The poor preservation of postclymeniids in the Hangenberg Black Shale requires a careful taxonomic approach (Zhang et al. 2019). Therefore, such specimens should be identified as Post. cf. evoluta (Fig. 3k). Currently, there is no proof that Post. nigra occurs in the typical (lower) Hangenberg Black Shale or Lower Crisis Interval. Therefore, it is not recognised as an alternative zonal index (compare the zonation of Korn 2000). In Section WJ at Drewer, Post. nigra even overlaps with Pr. kockeli.

The rare prionoceratids from the Hangenberg Black Shale are too poorly preserved for a reliable identification. Paul (1937b, p. 751) mentioned a large-sized “Imitoceras” from Velbert, which, unfortunately, was never described or illustrated. Based on the discovery of very early Ac. (Stockumites) sp. in Hangenberg Black Shale equivalents of southern Morocco (Klug et al. 2016), the presence of the genus at this level in the Rhenish Massif is possible, too. Very restricted evidence comes from a pyritic and septarian-rich marl with Ac. (Stockumites) sp. at the B224 building site (Bed 05/30, Korn 1992b), which overlay as a deepening unit oncoid-bearing neritic strata but which correlation with the Hangenberg Black Shale level is very tentative.

Conodont correlation: The base of the Post. evoluta Zone correlates with the base of the ckI.

Acutimitoceras (Stockumites) prorsum Zone (UD I-F to LC I-A1)

Reference sections: B224 building site near Aprath (Bed 06/1), Am Haken Brickwork Quarry (pyritic black shale), Hasselbachtal (Beds 85H–81H), Apricke (Bed 2H), Oberrödinghausen (Hangenberg Shale, Sacher-Beds 226a–b), Wocklum (Beds 2–5b), Effenberg (Beds 18b–c), Stockum (Beds 103 and 100), Drewer (Bed 95 = Hangenberg Sandstone, Beds 97–100 = Stockum Level Black Shale, Beds 1 and 1/2 = 13d = Lower Stockum Limestone, Bed 2= 13c = ?Upper Stockum Limestone).

Other marker species: Acutimitoceras (St). cf. procedens, Ac. (St.) subbilobatum (auct.), Ac. (St.) intermedium (auct.), Ac. (St.) aff. antecedens, Ac. (St.) kleinerae, Ac. (St.) stockumense, Ac. (Str.) caesari, Ac. (Str.) carinatum.

Discussion, subdivision, and conodont correlation: Specimens from the Hangenberg Shale/Sandstone are squashed, which makes their precise identification arbitrary. Therefore, it is difficult to establish a species succession within the total, relatively long interval. Based on the litho- and event stratigraphy in combination with conodont and/or spore data, there are currently five successive goniatite levels within the zone (marking the current knowledge of staged entries in bold):

1. Basal part (Middle Crisis Interval I, basal UD VI-F, lower Hangenberg Shale)

Ac. (Stockumites) sp. (?intermediate from Mimimitoceras, with still relatively low whorls) and Postclymenia sp. from 42 cm above the base of the Hangenberg Shale at Oberrödinghausen (Becker et al. 2016a).

2. Lower part (Middle Crisis Interval II, main UD VI-F, upper part of Hangenberg Shale/Hangenberg Sandstone):

Ac. (St.) cf. procedens and Ac. (St.) aff. antecedens (as evolute as in the prorsum Group) from ca. 3.8 m above the base (= 2.2 m below top) of the Hangenberg Shale at Oberröding-hausen (Becker et al. 2016a).

Ac. (St.) cf. subbilobatum (auct.) from 1.1 m below the top of the Hangenberg Shale at Oberrödinghausen (Luppold et al. 1994).

Ac. (St.) cf. procedens from 25 cm below the top of the Hangenberg Shale at Oberrödinghausen (Paproth and Streel 1970: Imitoceras (Prionoceras ?) sp., pl. 24, figs. 1a–1b).

Ac. (St.) cf. procedens (e.g. Becker et al. 2016a: fig. 6.3) and Ac. (St.) prorsum Group (see Korn et al. 1994: fig. 18I) in the Hangenberg Sandstone (Bed 95) at Drewer.

3. Middle part (Upper Crisis Interval I, upper UD VI-F, basal Stockum Limestone and shale equivalents still without Pr. kockeli, ckI)

Post. nigra and Post. evoluta from limestones nodules in the lower part of the Stockum Level Black Shale (Bed 97) at Drewer (Korn 1991; Korn et al. 1994b).

4. Upper part (Upper Crisis Interval II, UD VI-F/LC I-A1, depending on the future GSSP position, Lower Stockum Limestone and equivalents with Pr. kockeli)

Ac. (St.) subbilobatum (auct.) and Ac. (Stockumites) sp. (including Ac. (St.) cf. prorsum of Becker 1988 and Ac. acutum of Korn 1993 and Luppold et al. 1994) from the dark-grey, calcareous top of the Hangenberg Shale (Stockum Level Black Shale) at Hasselbachtal (Bed 85).

Post. nigra, Post. evoluta, Ac. (St.) intermedium (auct.), and Ac. (St.) cf. prorsum from limestone nodules in the upper part of the Stockum Level Black Shale (Bed 100) at Drewer (Korn 1991; Korn et al. 1994b).

Ac. (Str.) carinatum in the Lower Stockum Limestone (Beds 1 and 1/2) at Drewer (Korn et al. 1994b; Becker et al. 2016b).

Ac. (Str.) carinatum, Ac. (Str.) caesari, and Ac. (St.) kleinerae in the probable Lower Stockum Limestone of section Steinberg Brook (B224 building site, Korn 1992b).

Ac. (Str.) cf. carinatum and Ac. (Stockumites) sp. in Bed 2H (38; Lower Stockum Limestone) at Apricke.

Unspecified acutimitoceratid assemblage of Effenberg (Beds 18b–c).

Ac. (St.) prorsum, Ac. (St.) stockumense, Ac. (St.) subbilobatum (auct.), Ac. (St.) intermedium (auct.), Ac. (St.) kleinerae, Ac. (Str.) carinatum, and Ac. (Str.) caesari from the type Stockum Limestone (Bed 103, upper part of Pr. kockeli Zone) of Stockum (Schmidt 1924a; Korn 1984, 1994).

5. Uppermost part (Upper Crisis Interval III, LC I-A1, Upper Stockum Limestone with Pr. kuehni):

Abundand juvenile acutimitoceratids from the Upper Stockum Limestone (Bed 100) at Stockum (Pr. kuehni recorded by Alberti et al. 1974: Sample 330).

Ac. (St.) intermedium (auct.), Ac. (St.) subbilobatum (auct.), Ac. (St.) kleinerae, and Ac. (Str.) carinatum from the lower part of the Upper Stockum Limestone (Bed 3a) at Müssenberg (Korn 1993; Luppold et al. 1994).

Ac. (St.) stockumense, Ac. (St.) procedens, Ac. (St.) kleinerae, Ac. (St.) intermedium (auct.), Ac. (St.) subbilobatum (auct.), and Ac. (Str.) carinatum from the upper part of the Upper Stockum Limestone (Bed 3A) at Müssenberg (Luppold et al. 1984; Korn 1993).

Ac. (St.) intermedium (auct.) and the youngest Rhenish clymeniid, C. striata, from the top of the Stockum Limestone at Müssenberg (Luppold et al. 1984; Korn 1989, 1993).

This summary suggests that Ac. (Str.) carinatum, Ac. (Str.) caesari, Ac. (St.) kleinerae, and Ac. (St.) stockumense may have potential for a future subdivision of the Ac. (St.) prorsum Zone. However, this is based on combined evidence, not on a locality with a faunal sequence. Therefore, we regard the current knowledge as too premature to propose subzones. The type level of the poorly known Ac. (St.) infracarbonicum (Paeckelmann, 1913) in the former Am Haken Brickwork Quarry of the Wuppertal region probably falls in the Upper Crisis Interval but cannot be placed with any precision. The taxonomic identity of Rhenish Ac. (St.) subbilobatum and Ac. (St.) intermedium with the types from Franconia requires modern studies of ontogenetic morphometry.

Gattendorfia subinvoluta Zone and Subzone (Vöhringer 1960, LC I-A2)

Synonym: Acutimitoceras (Acutimitoceras) acutum Zone (Vöhringer 1960).

Reference sections: Oberrödinghausen (Beds 6b–6a), Hasselbachtal (Beds 80H–73H), Müssenberg (Bed 3C-2), Drewer (Bed 3).

Other marker species: Acutimitoceras (A.) acutum (Oberrödinghausen, Bed 6), Wey. reticula (Oberrödinghausen, Bed 6), “G.costata (Hasselbachtal, Bed 80, Korn and Weyer 2003), G. involuta (Oberrödinghausen, new record from the upper part of Bed 6), H. sphaeroidalis (Oberrödinghausen, Bed 6), Ac. (St.) undulatum (Oberrödinghausen, Bed 6), Ac. (St.) antecedens (Oberrödinghausen, Bed 6), Ac. (St.) convexum (Oberrödinghausen, Bed 6), “Mim.simile (Hasselbachtal, cf. Bed 80).

Discussion: As noted in the taxonomic appendix, there are morphological differences between the types of G. subinvoluta from Franconia and assumed Rhenish representatives of the species. This may reflect the biogeographic separation by a narrow oceanic system.

Conodont correlation: The base of the zone falls in the ca. middle part of the S. (Eo.) sulcata s.l./Pr. kuehni Zone (Hasselbachtal, Bed 80; Drewer, Bed 3a).

“Eocanites” nodosus Subzone (new, LC I-A3)

Reference sections: Oberrödinghausen Railway Cut (Beds 5c–5a), Hasselbachtal (Beds 72H–ca. 62H), Müssenberg (Bed 1), Drewer (Beds 3a–5a).

Other markers: Voehringerites peracutus (Oberrödinghausen, Beds 5c–5a2, Becker and Weyer 2004; Hasselbachtal, Bed 72H), Ac. (Str.) heterolobatum (Oberrödinghausen, Bed 5), N. trochiforme (Oberrödinghausen, Bed 5), N. subacre (Oberrödinghausen, Bed 5), “Wey.concava (Oberrödinghausen, Bed 5).

Discussion: The “Eoc.nodosus Group differs in its square, rectangular to sulcate cross-sections clearly from the typical, younger Eoc. supradevonicus Group, which is characterised by well-rounded whorls. This should be used for a distinction at generic level.

Conodont correlation: At Drewer (Bed 3a), the oldest Eocanites sp. pre-dates the FAD of S. (Eo.) bransoni. At Hasselbachtal, V. peracutus and “Eoc.nodosus occur in the lower part of the S. (Eo.) bransoni Zone. At Oberrödinghausen, V. peracutus is recorded from the top of the S. (Eo.) sulcata s.l./Pr. kuehni to the lower S. (Eo.) bransoni Zone (Becker and Weyer 2004). Much younger (level with Ps. triangulus triangulus) is the supposed V. peracutus from Müssenberg (Bed 1, Luppold et al. 1994), which likely affinities with the Karagandoceratidae have been raised by Korn and Weyer (2003, p. 99) and Becker and Weyer (2004, p. 29).

Paprothites dorsoplanus Zone and Subzone (Vöhringer 1960, LC I-B1)

Reference sections: Oberrödinghausen Railway Cut (Beds 4b–4a), Hasselbachtal (Beds ?59H–58H).

Other marker species: Globimitoceras globiforme (Oberröding-hausen, Bed 4), H. multisulcata (Oberrödinghausen, Bed 4), “Mim.exile (Oberrödinghausen, Bed 4).

Conodont correlation: At Hasselbachtal and Oberrödinghausen, the base of the zone corresponds closely to the base of the S. (S.) duplicata Zone.

Paragattendorfia sphaeroides Subzone (new, LC I-B2)

Reference sections: Oberrödinghausen Railway Cut (Beds 3e–3d1), Hasselbachtal (Beds 57H–51H, see Korn and Weyer 2003), Oese (Korn-Beds 22–27 = Kaiser-Beds 16–19).

Other marker species: Costimitoceras ornatum (Ober-rödinghausen, Bed 3e), H. gracilis (Oberrödinghausen, Bed 3d; Hasselbachtal, Bed 57H), Wey. molaris (Oberrödinghausen, Bed 3e; Hasselbachtal, Bed 57H), Pap. raricostatus (Oberrödinghausen, Bed 3d), Pap. ruzhencevi (Hasselbachtal, Bed 57H), Paragattendorfia n. sp. II of Korn and Weyer (2003; Oese, Korn-Bed 22 between Beds L and M).

Discussion: It is possible that Parag. sphaeroides Weyer, 1972 is a junior synonym of the poorly known type species of the genus, Parag. humilis Schindewolf, 1924. If this is confirmed, the subzone name will have to be changed. An involute variant with slightly higher whorls than in typical specimens, Parag. cf. sphaeroides, is illustrated in Fig. 3n–o.

Conodont correlation: At Oberrödinghausen, the zonal base lies in Bed 3e below the FOD of several indicators of the higher S. (S.) mehli Zone (in Bed 3d2 = Voges-Sample 10 = Ziegler-Bed 10), such as S. (S.) cf. wilberti, S. (S.) lobata M1, S. (S.) belkai M2, and S. (S.) obsoleta. The Hasselbachtal record from Bed 57H post-dates the first S. (S.) cooperi (M2), which indicates a position above the base of the S. (S.) mehli Zone. At Oese, the Paprothites-Paragattendorfia fauna (Korn-Bed 22 = Kaiser-Bed 16) is not well dated by conodonts. Siphonodella (S.) belkai M1, an indicator for the S. (S.) mehli Zone, was recorded by Kaiser et al. (2017) from just above (Kaiser-Bed 17).

Pseudarietites westfalicus Zone (Vöhringer 1960, LC I-C)

Reference sections: Oberrödinghausen Railway Cut (Beds 3c2–3a), Hasselbachtal (Bed 49H), Oese (Korn-Beds 28 to ca. 33 or higher), Drewer (Bed 10).

Other marker species: Pseudarietites subtilis (Oberrödinghausen, Bed 3c; cf. Oese, Korn-Bed 28), Eoc. brevis (Oberrödinghausen, Bed 3c), Eoc. tener (Oberrödinghausen, Bed 3c), Eoc. spiratissimus (Oberrödinghausen, Bed 3c).

Subdivision: At Oberrödinghausen, a range of taxa enter somewhat higher in the zone, which may enable the separation of an upper or G. crassa Subzone (Beds 3b–3a, LC I-C2). Characteristic at this higher level are Kaz. evoluta, N. acre, Ac. (St.) depressum, and Pseud. carinatus (here transferred from Eocanites because of its concave ribs, keel, and Pseudarietites-type sutures). An entry of Kaz. evoluta above the oldest Pseudarietites is also known from Oese (Korn and Weyer 2003, Korn-Bed 30). Pseudarietites planissimus occurs at Oberrödinghausen near the top of the westfalicus Zone (see Korn 2006). A fauna with G. crassa has also been mentioned from the Attendorn-Elspe Syncline (Weber 1934).

Conodont correlation: At Oberrödinghausen, the base of the zone lies in the middle between the FODs of S. (S.) obsoleta and Ps. triangulus triangulus, ca. in middle to higher parts of the S. (S.) mehli Zone. The zonal occurrences at Hasselbachtal and Oese belong also to this time interval. The levels with Kaz. evoluta at Oberrödinghausen and Oese are still within the same conodont zone.

Paragattendorfia patens Zone (LC I-D)

Reference sections: Oberrödinghausen Railway Cut (Beds 2b–1a), Oese (Korn-Beds 36–38).

Other marker species: Eocanites supradevonicus (Ober-rödinghausen, Bed 2; Oese, Bed S = Korn-Bed 36, Kullmann in Becker et al. 1993). Korn and Weyer (2003), however, noted an Eoc. cf. supradevonicus already lower at Hasselbachtal (Bed 51H), in association with the last local Paprothites (top LC I-B). Following Korn (2006, fig. 2), Paralytoceras crispum enters at Oberrödinghausen at the base of the patens Zone.

Subdivision: The entries of Eoc. planus and Pseud. serratus in Bed 1 of Oberrödinghausen can possibly be used to define an upper subzone. However, since the type level is relatively poor in fauna (Vöhringer 1960), additional data are needed. Korn (1988a) described an isolated corresponding faunule with Pseud. cf. serratus from Hoppecke in the eastern Sauerland.

Conodont correlation: At Oberrödinghausen, the base of the zone slightly post-dates the base of the S. (S.) sandbergi Zone (Bed 3a, Korn and Weyer 2003). In the absence of index conodonts, the beds with Eoc. supradevonicus at Oese cannot be correlated with precision. The entry of Pseud. serratus in the upper part of the Parag. patens Zone pre-dates at Oberrödinghausen the FOD of S. (S.) lobata M1 (in Bed 1a = Ziegler Bed 17 = Voges Sample 11).

LC I-E

North African goniatite successions (eastern Anti-Atlas: Ebbighausen and Bockwinkel 2007, southern Algeria: Ebbighausen et al. 2004) showed the existence of a fifth lower Tournaisian zone (LC I-E) with the index genus Kahlacanites below the Lower Alum Shale Event Interval at the base of the middle Tournaisian (basal Tn 2 of classical substage subdivision). There are no corresponding goniatite faunas from any European section. However, the top of the Rhenish Hangenberg Limestone is marked by a variably thick unfossiliferous shale unit. This should be regarded as an equivalent of the Gondwana Kahlacanites interval and may represent a long time interval.

Event stratigraphy (Fig. 1)

Kaiser et al. (2015) and Becker et al. (2016a) introduced informally a new terminology and subdivision of the extended Hangenberg Crisis Interval, which is formalised and refined here. Using lithostratigraphic units of the northern Rhenish Massif as examples/reference, the new scheme will add precision to global correlation and provide distinctive, unequivocal terms to be used during the ongoing GSSP search. Refined information from other regions may lead to the recognition of further event stratigraphical units. The subdivision of the Hangenberg Crisis Interval in the Rhenish Massif (from base to top) is as follows:

Crisis Prelude (initial regressive interval)

  1. Part I.

    Drewer Sandstone with Post. evoluta or increasing condensation and macrofossil accumulation in the upper Wocklum Limestone, top W. denckmanni Subzone (UD VI-D1); supposed equivalents in the neritic facies of the Velbert Anticline (see Paul 1937a, 1939a).

  2. Part II.

    Top Wocklum Limestone with Epi. applanata (UD VI-D2) and diverse pre-extinction faunas.

Lower Crisis Interval (transgressive and climatic warming interval)

  1. Part I.

    Hangenberg Mass Extinction (base UD VI-E, base ckI) with the sudden onset of anoxia/euxinia (local pyrite lags).

  2. Part II.

    Hangenberg Black Shale with restricted Post. cf. evoluta Fauna, basal LN Zone; supposed oxic equivalents with rich benthic fauna in the Velbert region (see sections of Paul 1939a).

Middle Crisis Interval (glacial regressive interval)

  1. Part I.

    Hangenberg Shale (greenish-grey) with basal Ac. (Stockumites) fauna (base UD VI-F).

- Sequence boundary -

  1. Part II.

    Hangenberg Sandstone, Seiler Conglomerate or lateral upper parts of the Hangenberg Shale, oolithic or neritic limestones, with Pr. meischneri and Pr. collinsoni (middle ckI), lower Ac. (Stockumites) faunas (middle UD VI-F).

Upper Crisis Interval (initial post-glacial transgressive interval)

  1. Part I.

    Basal Stockum Limestones (first limestones above Hangenberg Sandstone) or Stockum Level Black Shales (partly marly or with limestone nodules), still only with Pr. meischneri and Pr. collinsoni (upper ckI), middle Ac. (Stockumites) faunas (upper UD VI-F).

  2. Part II.

    Lower Stockum Limestones with Pr. kockeli (s.l.) or Stockum Level Black Shale (e.g. calcareous black shale of Hasselbachtal) with upper Ac. (Stockumites) faunas, locally with subdivisions. Slightly higher follows the LN/VI Zone boundary, the main terrestrial extinction level, possibly also the main extinction level in neritic facies, which lies above the Pr. kockeli FAD.

  3. Part III.

    Upper Stockum Limestones with Pr. kuehni and uppermost Ac. (Stockumites) faunas (current LC I-A1); S. (Eo.) sulcata s.l. may be rarely present; locally with encrinites or turbidites (subdivisions) at the base.

(local parasequence boundary)

Post-Crisis Interval

Basal part: Basal Hangenberg Limestone, overlap of S. (Eo.) sulcata s.l. and G. subinvoluta (LC I-A2) Zones.

Main part: Main Hangenberg Limestone, S. (S.) bransoni to S. (S.) sandbergi zones, Pap. dorsoplanus to Parag. patens Zones (LC I-B to D).

Stable isotope stratigraphy

In the Rhenish Massif, DCB carbon and oxygen stable isotope analyses were conducted bed-by-bed at Hasselbachtal (Figs. 4, 5), Oberrödinghausen (Fig. 5), and Oese (Kaiser 2005; Kaiser et al. 2006). Carbon isotopes of micrites (δ13Ccarb) and of sedimentary organic matter (δ13Corg) were used to reconstruct variations in the carbon isotope composition of the oceanic dissolved inorganic carbon pool. During marine anoxia, global black shale deposition (HBS), and enhanced organic carbon burial, a pronounced positive carbon isotope excursion (CIE) could be recorded at Hasselbachtal (Fig. 4). The CIE is well correlated with a CIE measured in black shales at Kronhofgraben (Carnic Alps), in continuous pelagic limestone successions at Grüne Schneid (Carnic Alps), as well as with positive peaks measured in several other distant regions worldwide (see review in Kaiser et al. 2015). Thus, carbon isotopes can be used as a chemostratigraphic tool to record the level of the anoxic Lower Crisis Interval (HBS) even when there are locally no black shales.

Fig. 4
figure4

Top-Devonian to basal Tournaisian carbon isotope values from carbonate (Ccarb) and organic matter (Corg) at Hasselbachtal, showing the marked positive excursion of the second starting in the Hangenberg Black Shale (basal ckI) and lasting into the marly Stockum Level Black Shale (ca. Protognathodus kockeli Zone) of Bed 85N (extracted and modified from Kaiser et al. 2006, fig. 6C, with simplified lithology of limestone nodules and nodular limestone in white, shale and siltstone in grey, black shale = Bed 115N, and dark-grey marl = Bed 85H). 1 = chronostratigraphy, 2 = ammonoid zonal key after Becker (1996), 3 = conodont zonation, 4 = bed numbers, 5 = lithology, TOC = total organic carbon.

Fig. 5
figure5

Pelagic sea surface palaeotemperatures (black dots and squares) calculated from oxygen isotope values of conodont phosphate from the uppermost Famennian and basal Tournaisian of Hasselbachtal (dots) and the Oberrödinghausen Railway Cut (squares), extracted and modified from Kaiser et al. (2006, fig. 7). 1  chronostratigraphy, 2  conodont zonation (compare Fig. 1 to understand abbreviations), 3  marker units, 4  sea-level curve; HBS Hangenberg Black Shale, HS Hangenberg Shale/Sandstone.

Conodont apatite is used for the analyses of δ18Ophosph because it has a high preservation potential of the primary isotopic signature and is considered to be unaffected by diagenesis. The oxygen isotopic composition of biogenic phosphate is dependent on temperature and composition of ambient seawater, and can be therefore used as a proxy for estimating sea-surface temperatures and salinity changes. The high abundance and high morphological diversity of conodonts provides a detailed bio- and chemostratigraphic resolution and the correlation of sections from different palaeogeographical realms. In this respect, the oxygen isotope values measured from Hasselbachtal, Oese, and Oberrödinghausen (Fig. 5) are similar to values from other sections in Spain (Pyrenees) and France (Montagne Noire). Slightly decreasing values from the Bi. ultimus ultimus Zone to the lower Tournaisian indicate a minor warming during the corresponding time span, if there was no influence of palaeosalinity, and without details for the intervening Hangenberg Crisis Interval. In the Rhenish Massif, no conodonts were available from the ckI. Records of a cooling episode, probably time-equivalent to the regressive Middle Crisis Interval, were observed in equivalent successions of the Carnic Alps (Kaiser et al. 2006).

Sequence stratigraphy

The successions of the Rhenish Massif have been used as a reference for DCB sequence stratigraphy (Van Steenwinkel 1993; Bless et al. 1993; Kaiser et al. 2011, 2015). A gradual shallowing upwards of the depositional environments is evident in the upper part of the Wocklum Limestone by increasing condensation (reduced sedimentation rates), a consequently strongly increasing fossil content, and by the return of shallow pelagic taxa, such as large-eyed trilobites or tabulate corals (Becker et al. 2016b). This highstand episode was followed by the local “Drewer Sandstone” (Crisis Prelude I, Fig. 1), which can be regarded as a lowstand deposit and its base represents a (para)sequence boundary. In the neritic realm of the eastern Velbert Anticline (Fig. 6), there are correlative pre-Crisis oolites and sandy beds, changing laterally (Wuppertal region) into red shales, marls, and limestones (Am Haken Brickwork Quarry). In several Sauerland sections (Dasberg, Reigern, Kattensiepen), the upper part of the Wocklumian falls in a time of current-induced non-deposition (Fig. 7). The shallowing at the “Drewer Sandstone” level can be recognised in many parts of the world and represents a global pre-Crisis sea-level drop (Kaiser et al. 2011, 2015), possibly related to an initial glacial cooling.

Fig. 6
figure6

Summary of facies developments in DCB sections of the Aachen, Velbert, and Wuppertal to Hemer regions. Bin Binsfeldhammer, SSW Süchtel-Sittard Well, Crom Ratingen-Cromford, KlSt Klein-Steinkothen, Vel 4 Velbert 4 Well, Lang Langenhorst, B224 B224 section near Aprath, Hak former Am Haken Brickwork Quarry, Rie Riescheid, Hass Hasselbachtal, Seil Seiler N of Iserlohn, Oese B7 road cut at Hemer-Oese, Apr Hemer-Apricke; HBS Hangenberg Black Shale, HS Hangenberg Shale, HSS Hangenberg Sandstone, St Stockum Limestone, SLBS Stockum Level Black Shale, Upp. Mbr. Upper Member (of Seiler Formation), LAS Lower Alum Shale, LASE Lower Alum Shale Event, “1” to “3” = correlation levels sensu Clausen et al. (1989a); ammonoid zonal key (e.g. VI-B, I-C) as explained in the text, ckI costatus-kockeli Interregnum, kock. kockeli, brans. bransoni, dupl. duplicata, sdbg. sandbergi, lob. lobata M1, cren. crenulata, m. T. middle Tournaisian

Fig. 7
figure7

Summary of facies developments in DCB sections of the Sauerland and northern subsurface (section numbering as in the text). Obrh Oberrhödinghausen Railway Cut, Hang Hangenberg, Dasb Dasberg, Eff Effenberg, Muess Müssenberg, Reig Reigern Quarry near Hachen, Stock Stockum Trenches (mostly Trench II), Wen section E of Weninghausen, Drew Provincial Quarry Drewer, Katt Kattensiepen Quarry, Eul Eulenspiegel, Scharf Scharfenberg, Ving Vingerhoets 93 Well near Oelde. For other abbreviations, see Fig. 6.

The Hangenberg Black Shale and its less anoxic, grey to greenish equivalents in western sections (Cromford, Velbert 4 Well, B224 near Aprath; Fig. 6) represent a sudden transgressive episode and phase of maximum flooding, defining the Lower Crisis Interval. The pyrite-enriched, often sharp base of the black shales suggests an anoxic marine flooding surface at the base of a TST, which is the level of the main Hangenberg Extinction, at least in the pelagic realm. The transgressive nature of the HBS is underlined by sections, where greenish, dark-grey, or black (hemi)pelagic shales, often with Post. cf. evoluta, overly shallow-water strata, such as neritic limestones (Cromford, Velbert 4 Well, Fig. 6), oncoidal siltstones (B224 near Aprath, Fig. 6), or sandstones (Vingerhoets 93 Well, Fig. 7). Similar patterns can be seen on other continents (Kaiser et al. 2015; Zhang et al. 2019).

The gradual change from the HBS to greenish and silty shale marks the slowing of sea-level rise to beginning sea-level fall and regression. The Hangenberg Shale is a pelagic highstand deposit (FSST) still low in the LN miospore Zone (Middle Crisis Interval I).

A subsequent main lowstand phase (LST) is represented by the locally increasing influx of coarser clastic sediments, the Hangenberg Sandstone, and its equivalents, such as siltstones (Drewer, Borkewehr) or thick, re-sedimented oolitic conglomerates and siliciclastics of the Seiler area (Fig. 7). A sequence boundary is placed at the base of the sandstones, conglomerates, or reworked oolites. The latter represents basin floor fans and incised valley fills above marine unconformities (e.g. Van Steenwinkel 1993). Herbig (2016) used the Hangenberg Sandstone base to define his Sequence 1. Both in the western realm (Aachen region: Binsfeldhammer, Velbert Anticline: Langenhorst; Fig. 6) and in the deeper facies of the Sauerland (Müssenberg, Kattensiepen, Drewer; Fig. 7), the sea-level fall caused gaps due to erosion and/or non-deposition. The partly much thicker HSS equivalent clastic deposits of other regions and continents correspond with a maximum lowstand (LST) in the higher LN miospore Zone and upper ckI (Middle Crisis Interval II).

In the eastern Rhenish Massif, the Upper Crisis Interval (DCB interval) is characterised by a return to carbonate sedimentation and condensed, fully pelagic conditions. This transgressive (TST) interval is characterised by the polyphase Stockum Limestone deposits, including some turbiditic limestones (Hasselbachtal, Oese, Apricke; Fig. 7), or by partially correlative, pyritic, or organic-rich Stockum Level Black Shales (SLBS, Am Haken Brickwork Quarry, Hasselbachtal; Figs. 6, 7), sometimes with embedded, fossiliferous limestone nodules (B224 near Aprath, Drewer). For the precise DCB positioning and correlation, it is important to realise that the first limestone level above the HS/HSS is locally of variable age (Fig. 7), from the top ckI with Pr. collinsoni (Drewer, ?Eulenspiegel; Upper Crisis Interval I), to the Pr. kockeli (Oese, Apricke, Hangenberg, Stockum; Upper Crisis Interval II) or even S. (Eo.) sulcata s.l./Pr. kuehni Zone (Hasselbach-tal; Upper Crisis Interval III). In the neritic Ardennes and Aachen region (western Rhenish Massif), the shallow-water limestones of the basal Hastière Formation begin with the Pr. kockeli Zone. But at the Velbert Anticline, the lack of conodonts prevents the precise dating of the basal Steinkothen and oolithic Laupen Members. Locally, there is evidence for a minor sea-level fall separating Lower and Upper Stockum Limestones (Lower and Upper Proto-gnathodus levels, Upper Crisis Intervals II and III; Fig. 7), or marls with Ac. (Stockumites) faunas and the latter (Hasselbachtal; Fig. 6). It caused the minor unconformity in the Oberrödinghausen Railway Cut, which disqualified it as DCB stratotype. A slightly younger reworking phase may lie at the base of the Hangenberg Limestone (Drewer), within the S. (Eo.) sulcata s.l./Pr. kuehni Zone; it marks the end of the Upper Crisis Interval.

The polyphase top-Devonian to basal Tournaisian (basal Mississippian) transgression (Sequence 1 of Herbig 2016) is well expressed on a global scale (Kaiser et al. 2015). The Hangenberg Limestone represents a highstand interval (HST), in which the fossil content becomes gradually sparser, changing eventually into a shaly interval. The sharp base of the anoxic to euxinic, basal middle Tournaisian Lower Alum Shale (LAS) represents the very sudden onset of a second Lower Carboniferous TST (base of Sequence 2 of Herbig 2016). It is equally distinctive in the western neritic realm, where it is expressed by the less anoxic and party fossiliferous Pont d’Arcole Formation that drowned the Hastière Formation carbonate platform (Fig. 6).

Trace element geochemistry, magnetic susceptibility, and cyclostratigraphy

Trace element geochemistry and gamma ray spectroscopy (CGR values) are important tools to reconstruct changes of detrital discharge, redox conditions (U/Th), and palaeo-productivity around the DCB. Magnetic susceptibility (MS) logging provides insights into changes of sedimen-tation, especially in relation to sea-level change. These methods, therefore, complement litho- and sequence stratigraphy. In addition, they are most useful to delineate cyclostratigraphic patterns, which are strongly expressed in the Wocklum and Hangenberg Limestones. For refined cyclostratigraphic correlations, it will be most important to tie each cycle to precise bed numberings and the biostratigraphical scales (see Korn and Weyer 2003). Kumpan et al. (2015), Becker et al. (2016b), and Hartenfels et al. (2017a, b) provided relevant data for four Rhenish DCB sections: Oese, Oberrödinghausen, Drewer, and Borkewehr. They support the general interpretations of sedimentary environment, microfacies, palaeoecology, sea-level changes, and event patterns as summarised by Kaiser et al. (2015).

Section descriptions

Aachen region and Niederrhein

In terms of sedimentation and lithostratigraphy, the DCB transition of the Aachen region continues the shallow-water setting of the eastern Ardennes. The Belgian formation terminology (e.g. Bultynck and Dejonghe 2002; Poty et al. 2002) can be largely adopted. The term Dolhain Formation, used for equivalents of the Etroeungt Formation in the Vesdre Nappe of Belgium (e.g. Bultynck and Dejonghe 2002), has not yet been accepted on the German side (e.g. Amler and Herbig 2006; Kasig and Reissner 2008). Currently, the only moderately good DCB outcrop is at Binsfeldhammer in the Burgholz Syncline.

Binsfeldhammer (Fig. 6)

Location: Slope of the road cut branching off from the Volberg-Vicht road towards Hastenrath, west of the middle/upper Tournaisian Binsfeldhammer Quarry, at r 2 516 900, h 5 624 800 on topographic sheet 5203 Stolberg (Fig. 8).

Fig. 8
figure8

Geographic location of the Binsfeldhammer DCB section in the Aachen region of the western Rhenish Massif (extracted and re-drawn from Walter 2010, fig. 14)

Literature: Paul (1937a: type locality of Syringopora (Vaughanites) flabelliformis), unpublished Ph.D. Thesis by Reissner (1990), Kasig and Reissner (2008: section log), Amler and Herbig (2006: type section of the Binsfeldhammer Subformation = Member). For more literature, see the review by Becker and Weber (2016).

Summary of succession:

Pont d’Arcole Formation (previously “peracuta Shale” or “Zwischenschiefer”): Unfossiliferous dark shales, with the major deepening of the Lower Alum Shale Event at the base; middle Tournaisian.

Hastière Formation, Binsfeldhammer Member: Ca. 3.5 m of cross-bedded dolomites with rare syringoporid corals above the last level with stromatoporoids; with Pr. kockeli in the lower part and S. (S.) duplicata in the higher part in the lateral Neu-Moresnet section (Reissner 1990). Age: Pr. kockeli Zone (Upper Crisis Interval) to top of lower Tournaisian. Our new sampling at Binsfeldhammer did not produce any conodonts.

- unconformity -

Etroeungt Formation (= Dolhain Formation):

Upper part: Thick-bedded dolomites with numerous relict structures of stromatoporids (indet.), the youngest known from the Rhenish Massif, rugose and syringoporid corals. Repeated sampling did not produce conodonts.

Lower to middle parts: Calcareous shales, thin-bedded limestones and thin- to thick-bedded dolomites with brachiopods, corals, stromatoporids, and foraminifers. Quasiendothyra kobeitusana, the index species of the DFZ 7 and for the uppermost Famennian, begins ca. 9 m below the top of the formation.

Discussion: Dolomitisation and poor outcrop conditions prevent an easy recognition of the unconformity. However, there is locally no evidence for sediments of the Lower/Middle Crisis Interval. The Hangenberg Regression may have led to erosion and/or non-deposition. The presence of an unconformity was supported by the analysis and correlation of coral faunas (Weyer 2000). Mottequin and Poty (2014) mentioned from their adjacent Stolberg Section a 2m thick sandstone-siltstone unit overlying Etroeungt (= Dolhain Fm.) dolomites. This unit, which is unknown at Binsfeldhammer, was interpreted by them as HSS equivalent.

Niederrhein subsurface, Süchteln-Sittard Well 1 (Fig. 6)

Location: Topographic sheet 4704 Viersen, r 2 526 830, h 5 682 220 (Fig. 9).

Fig. 9
figure9

Geographic location of DCB sections in the Bergisches Land (Velbert Anticline and Wuppertal area) and Sauerland (section numbering as in the text). 2 Süchtel-Sittard Well, 3 Ratingen-Cromford, 4 Klein-Steinkothen, 5 Hefel, 6 Velbert 4 Well, 7 Langenhorst, 8 B224 near Aprath, 9 Am Haken Brickwork Quarry, 10 Riescheid, 11 Hasselbachtal, 12 Seiler N of Iserlohn, 13 Oese, 14 Apricke, 15 Oberrödinghausen Railway Cut, 16 Hangenberg, 17 Dasberg, 18 Effenberg, 19 Müssenberg, 20 Reigern Quarry near Hachen, 21 Borkewehr/Wocklum, 22 Stockum Trenches, 23 Weninghausen, 24 Drewer, 25 Kattensiepen, 26 Bilstein Cave, 27 Eulenspiegel, 28 Scharfenberg, 30 Grimmighausen. The Vingerhoets 93 Well (loc. 29) lies far outside the map in the subsurface of the eastern Münster Basin, ca. 40 km NNW of Drewer = Loc. 24 (for a detailed map see Clausen 2008)

Literature: Bless et al. (1998), Ribbert (1998, 2008).

Summary of succession: Bless et al. (1998) described the DCB succession that was reached in a borehole in the Krefeld region (Niederhein) between ca. 224 and 265 m depth. It resembled both the Aachen and Velbert regions. It can be summarised as follows, re-assigning the strata to currently used lithostratigraphic units:

Pont d’Arcole Formation: 227.0–231.5 m, bluish-grey, calcareous and pyritic shales, intercalated by two levels of dolomitic limestone with foraminifers (e.g. Chernyshinella glomiformis), ostracods and rare trilobites, middle Tournai-sian, Lower Alum Shale Event Interval.

Hastière Formation (“Lower Dolomite” = Steinkothen Member): 231.5–243.0 m, bluish-grey, partly dolomitised and peloidal limestone, in the lower part with an interval of micaceous and calcareous sandstones, with crinoids, ostracods (Pseudoleperditia), and rare foraminifers (Bisphaera, Earlandia, Diplosphaerina, Endothyra), lower Tournaisian, Middle/Upper or post-Crisis Interval.

Hangenberg Shale equivalent: 243.0–244.5 m, bluish-grey, calcareous shale, Crisis Interval, undifferentiated.

Etroeungt Formation (= Dolhain Formation):

244.5–251.7 m, dark-grey shallow-water crinoidal limestone (grain- and rudstones) with rugose corals (Campophyllum, “Palaeosmilia”, Syringaxon, metriophyllids), syringoporids, a michelinid, stromatoporids, brachiopods, bryozoans, gastropods, ostracods, trilobites (Omegops), calcareous algae, miospores (Retispora lepidophyta), and foraminifers (Quasiendothyra kobeitusana), uppermost Famennian, pre-Crisis Interval.

251.7–258.7 m, dark-grey, silty, laminated shale, with an intercalated unit of crinoid limestone with brachiopods, syringoporids, rare stromatoporids, gastropods, ostracods, eridostracans (Cryptophyllus), calcareous algae, and foraminifers (Q. aff. kobeitusana), uppermost Famennian.

258.7–259.8 m, bluish-grey limestone and marl with corals (syringoporids, Campophyllum, heterocorals), stromatoporids (Atelodictyon ratingense, Amphipora), calcareous algae, ostracods, and foraminifers (Q. aff. kobeitusana), lower part of uppermost Famennian, transgressive on upper Famennian sandstones (= Evieux Formation).

Discussion: The separation of the Etroeungt and Hastière Formations by a shale unit is not known from the Aachen region and suggests an intermediate palaeogeographic position towards the Velbert region, despite the assumed barrier of a Krefeld High. The latter had probably a different outline than shown in most reconstructions (see brief discussion in Becker et al. 2016b). It is possible that the sandstones intercalated within the “Lower Dolomite” correlate with the Hangenberg Sandstone (Middle Crisis Interval) but the available biostratigraphic data are too sparse for a reliable interpretation.

Velbert Anticline

DCB successions along the northern margin of the Velbert Anticline are characterised by a lateral facies transition (e.g. Franke et al. 1975; Herbig et al. 2001). The upper part of the thick Velbert Formation is characterised in the Ratingen area by the increasing intercalation of limestones with neritic fauna, such as rugose corals, brachiopods, phacopids, stromatoporids, ostracods, and foraminifers. Following Drevermann (1902), Bärtling and Paeckelmann (1928) and Paul (1939a), the term Etroeungt Member is revived for this succession (the former “Etroeungt-Schichten”). It is not wise to neglect this interval of reduced clastic input within an undivided Velbert Formation due to its importance for correlation towards the Ardennes. Because it is unsuitable as a mapping unit, it cannot be separated regionally as a full formation, unlike as in the Ardennes. Future facies and faunal studies may support a lithostratigraphic differentiation between the type Etroeungt Formation of the southern Dinant Syncline, the dolomitised neritic facies settings of the Vesdre-Aachen region (proposed Dolhain Formation), and the Velbert Anticline. There, the term “Angertal Schichten” was established as a lower subdivision of his Etroeungt by Paul (1939a) on faunal, not on lithological, grounds, but it is principially available as a member name if neritic workers agree on a lithostratigraphical definition and type section. As outlined by Amler and Herbig (2006), the uppermost Famennian limestones grade east of Heiligenhaus into a siliciclastic facies with an important influx of oolithic material, especially in the lower Tournaisian (Laupen Member). To the NNW of the Velbert Anticline, DCB beds were once also accessible at two small distinctive saddles of the Lintorf region (sheet 4607 Kettwig). For example, Paul (1938a) suggested the presence of Postclymenia in the Diepenbrock area.

Ratingen-Cromford (Fig. 6)

Location: Old, mostly water-filled quarry in the Angerbach Valley in a recreation area N of Ratingen (“Naturpark Blauer See”), NW end of exposed Velbert Anticline (Fig. 9), topographic sheet 4607 Heiligenhaus, r 2 560 000/h 5 686 160 (GPS N 51° 18′ 25.44″, E 6° 51′ 35.4″). An adjacent railway cut is the type locality of the Steinkothen Member (Amler and Herbig 2006) and formed the base for the initial bed-by-bed investigations of Paul (1939a).

Literature: Drevermann (1902: type locality of Phacops bergicus, Sphenotus? ratingensis, Prothyris bergica, and Euchondria vera), Nekhoroshev (1932: type locality of the bryozoans Orthopora bifurcata and Monotrypella (?) cromfordensis), Gallwitz (1932), Liebus (1932: early foraminifer records), Paul (1937a: type locality of Derbiya steinhagei, Clathrodictyon ratingense, Buxtonia paeckelmanni, Thomasina angusta, and Brachythyris ratingensis; 1938b, 1939a), Conil et al. (1964), Streel (1966, 1969), Conil and Paproth (1968), Paproth and Streel (1970, 1982), Franke et al. (1975), Paproth et al. (1976), Price and Korn (1989), Brauckmann (1990), Amler et al. (1994), Herbig et al. (2001), Aretz et al. (2006), Winkler-Prins and Amler (2006), Ernst et al. (2015).

Summary of succession: The section is well known since the original description by Paul (1939a). Water filled the quarry after it was abandoned, which rendered large parts of the outcrop difficult to access. As noted by Conil and Paproth (1968), there is exposure along the path leading from the park entry to the open-air stage. Coral- and bryozoan-rich beds of the Velbert Formation (Etroeungt Member) are easily accessible along a small paved track along the railway. The DCB interval is as follows:

Pont d’Arcole Formation (“Zwischenschiefer”): Ca. 2.5 m dark, laminated shales, siltstone, and marls with S. (S.) crenulata, S. (S.) quadruplicata, and other conodonts (S. (S.) crenulata Zone), spiriferids, productids and other brachiopods, middle Tournaisian, Lower Alum Shale Event Interval.

Hastière Formation, Steinkothen Member (type locality, “Ostracodenkalk”):

Beds 24–25, 14.85 m, dark-grey, micritic, argillaceous, partly dolomitic limestone with shale intercalations, crinoids, brachiopods (type level of Cyrtina ratingensis (Paul, 1937a), Piloricilla paeckelmanni (Paul, 1937a), and of the insufficiently known Thomasina angusta Paul, 1937a), abundant fenestellids, ostracods, and corals, at the top with S. (S.) lobata (S. (S.) lobata Subzone), still with Quasiendothyra (Conil et al. 1964, p. 62) and other foraminifers, Upper Crisis Interval to lower Tournaisian (post-Crisis Interval).

Hangenberg Shale/Sandstone:

Beds 23, 16 m grey-brown, sandy, micaceous shales and thin, platy, micaceous sandstones, Middle Crisis Interval.

Hangenberg Black Shale equivalent:

Bed 22, ca. 5m greenish-grey shales, occasionally with sandy lenses, bivalves (Guerichia), spiriferids (e.g. Sphenospira julii), productids (type level of Whidbornella caperata paeckelmanni (Paul, 1939a); Tornquistia polita), and Post. cf. evoluta (evoluta Zone, UD VI-E), Lower Crisis Interval in neritic, (sub)oxic, siliciclastic facies.

- 24 m gap (variably 12–28 m according to different authors) -

Velbert Formation, Etroeungt Member (“Angertal Schichten”):

Beds 20–21, 21.3 m dark-bluish-grey limestones and marls with diverse foraminifers (including Quasiendothyra and many others), ostracods (Cryptophyllus), trilobites (Omegops), bivalves, Post. cf. evoluta (“Striatoclymenia euryomphala” from Bed 21, Paul 1939a; UD VI-D), syringoporids, rugose corals (“Palaeosmiliaaquisgranensis), and calcimicrobes (Girvanella), pre-Crisis Interval and Crisis Prelude.

Beds 17–19, 13 m sandy and micaceous shale and thin sandstones, interrupted by ca. 1 m of dark-bluish-grey crinoidal limestone (Bed 18); with foraminifers, trilobites (Omegops), bivalves, gastropods (Naticopsis), brachiopods (productids, orthotetids: type level of Derbyia steinhagei Paul, 1937a, orthids, spiriferids, terebratulids), fenestellids, and spores (Retispora lepidophyta and many others, floral lists in Paproth and Streel 1970, p. 376, and Paproth and Streel 1982, p. 12; LL Zone).

Bed 16, 8.7 m light- to dark-grey, medium- to thick-bedded, solid crinoidal limestone with stromatoporids (type level of Clathrodictyon ratingense Paul, 1937a, pectinid bivalves, brachiopods, solitary rugose corals (“Palaeo-smiliaaquis-granensis), syringoporids, foraminifers (Quasiendothyra kobeitusana), pre-Crisis Interval, uppermost Famennian.

Discussion: It is very unfortunate that the critic interval, from very fossiliferous limestones of the assumed Crisis Prelude to the shale with Postclymenia and basal Hastière Formation, is currently not accessible. The Cromford section provided unique opportunities for the correlation and intergradation of Rhenish pelagic and neritic successions and for the understanding of DCB extinction patterns in the two shelf realms. As evident from the comments by Winkler-Prins and Amler (2006), the Cromford brachiopods require revision, which is true for most other faunal elements from the locality.

Paul (1939a) mentioned shales with Post. cf. evoluta from numerous other adjacent localities on sheet Kettwig: valley below Sondert, debris of the Thalburg Mine, Ruthen, Giesenhaus area, road slope between Roßdelle and Müllerbaum, valley end at Scharpenhaus, Herberg, and Steinloch Mine. It is remarkable that the pure or calcareous Postclymenia shales, the supposed shallow-water Hangenberg Black Shale equivalents, yielded also a rich, oxic neritic fauna, consisting of diverse brachiopods (productids, orthids, spiriferids, terebratulids), bivalves (pectinids, nuculids, Grammatodon), fenestellid bryozoans, and gastropods. It is especially regrettable that a directly underlying, 10 cm thick bluish-grey, crystalline limestone with numerous Postclymenia from Scharpenhaus (Paul 1939a, p. 676, Bed 2) cannot be sampled any more for conodonts, microfacies, or geochemistry.

Klein-Steinkothen (Fig. 6)

Location: Two small old, partly overgrown quarries in the Angerbach Valley E of Eggerscheidt and W of Ratingen-Hösel, NW flank of the Velbert Anticline (Fig. 9), topographic sheet 4607 Heiligenhaus, r 2 563 250/h 5 687 560 (GPS N 51° 19.129′, E 6° 54.425′).

Literature: Nekhoroshev (1932), Gallwitz (1932: type locality of Orthotetes wunstorfi, Chonetes ratingensis, Plicochonetes cromfordensis cromfordensis, and Pl. cromfordensis latus), Paul (1939a), Böger (1962), Conil et al. (1964), Streel (1966), Conil and Paproth (1968), Paproth and Streel (1982), Richter (1992), Amler et al. (1994), Amler and Herbig (2006: introduction of the Steinkothen-Subformation = Member), Denayer et al. (2011), Herbig et al. (2019).

Succession: There are remnants of two old limestone quarries, which are separated by an outcrop gap (ridge covered by wood) that is difficult to bridge by trenching. Unfortunately, intense re-sampling did not produce any conodonts from the neritic, shallow-water, mixed limestone-siliciclastic facies. The DCB interval can be summarised as follows (based on Herbig et al. 2019):

Hastière Formation, Steinkothen Member (“Ostracodenkalk”):

Beds 28.1 to 28.16, 6.5 m (up to 8.3 m) medium- to thick-bedded, dark, bluish to black, macrofossil-poor limestones with crinoids, ostracods, foraminifers, calcimicrobes (Issinella), rare rugose corals (Siphonophyllia at the top, new Campophyllum record from Bed 28–3), large-sized Quasiendothyra kobeitusana at the base (Conil and Paproth 1968), and with the zonally non-diagnostic Po. inornatus s.l. at the top (record of Böger 1962), ?Upper Crisis Interval to lower Tournaisian.

- 10–12 m gap -

Velbert Formation, Etroeungt Member:

Beds 27A–27G, 2.3-m limestone with foraminifers, brachiopods, solitary rugose corals (“Clisiophyllumomaliusi), abundant crinoid ossicles, and Bi. jugosus (Böger 1962), as an indicator of the pre-Crisis Interval.

Bed 26, 1.2 m silty, bluish-grey, micaceous shale.

Beds 22–25, 1.6 m silty limestones grading upwards into crystalline, crinoidal limestones with brachiopods, solitary rugose corals, and miospores (Retispora lepidophyta).

Beds 2–21, 9.15-m alternating calcareous siltstones and sandstones with some plant debris.

Beds 1A–1K, 5.6 m dark-bluish, sometimes nodular, crinoidal foraminifer grainstones (abundant Quasiendothyra, Paracalligeloides, Bisphaera, Diplosphaerina, Eotuberitina etc.) with calcimicrobes (Girvanella), stromatoporids, solitary rugose corals (Campophyllum, “Palaeosmiliaaquis-granensis), and brachiopods, uppermost Famennian.

Lateral section, beds below Bed 1 with a kosmoclymeniid (“Oxyclymenia” of Paul 1939a).

Discussion: It is intriguing that stromatoporids locally do not range to the top of the Velbert Formation. The presence of “Strunian”-type fossils (corals, quasiendothyrids) in the lower part of the Hastière Formation resembles the Cromford succession. It questions the precise extinction level of shallow-water faunas in relation to the pelagic extinction at the base of the Hangenberg Black Shale. Therefore, Denayer et al. (2019) suggested that neritic extinctions occurred on the Ardenne Shelf during the maximum regression (“Hangenberg Sandstone Event”). However, since Pr. kockeli enters already in the basal marker limestone of the Hastière Formation (e.g. Bouckaert and Groessens 1976), the survival of various neritic taxa lasted obviously well into the transgressive Upper Crisis Interval. This explains why at Klein-Steinkothen no major regression can be recognised within the exposed Hastière Formation above the level of the last quasiendothyrids and “Strunian”-type corals. In the absence of age-diagnostic conodonts or brachiopods, the timing and patterns of neritic extinction are locally difficult to resolve.

Hefel

Location: Disused, partly pond-filled old quarry N of Velbert (Fig. 9), a natural reserve, at the small settlement Hefel, sheet 4608 Velbert, r 2 573 340, h 5 691 780.

Literature: Bärtling and Paeckelmann (1928), Gallwitz (1932), Paul (1937a), Franke et al. (1975), Paproth et al. (1976), Paproth and Streel (1982), Herbig et al. (2001), Amler and Herbig (2006).

Succession: The 58 m thick succession ranges from the Etroeungt Member to the Richrath Formation. The DCB part is strongly condensed and incomplete. Paproth et al. (1976) illustrated two specimens of Post. cf. evoluta (as Cymaclymenia euryomphala) from a calcareous silt/sandstone at the base (Bed 1), which may correlate with the “Drewer Sandstone” (Crisis Prelude). This tentative interpretation is based on the fact that the Postclymenia level was overlain by probable Hangenberg Shale equivalents (Beds 4–6), followed by thin oolites (Beds 4–6, Laupen Member of Hastière Formation). The section requires new investigations but it is doubtful that the Postclymenia level is still accessible. For example, Amler and Herbig (2006) observed that the oolithic basal Laupen Member eroded into the top limestone of the “Strunian”.

Velbert 4 Well (Fig. 6)

Location and literature: NE end of Velbert Anticline (Fig. 9; see map in Herbig et al. 2014).

Succession: The well was regionally unique since it provided an almost complete core through the uppermost Famennian to upper Viséan of the region. The DCB interval was as follows:

Pont d’Arcole Formation: 1.4 m dark-grey shale with two carbonate beds, a bioclastic dolomite and an oncolithic brachiopod-bearing rudstone, middle Tournaisian, Lower Alum Shale Event Interval.

Hastière Formation, Laupen Member: 8 m oolithic and peloidal grainstone, lower Tournaisian.

- 0.5 m gap -

Hangenberg Sandstone: 10 m alternating grey shale and sandstone, Middle Crisis Interval II.

Hangenberg Shale: 3.5 m calcareous shale, Middle Crisis Interval I.

Hangenberg Black Shale: 1 m irregularly laminated grey shale, Lower Crisis Interval.

Velbert Formation, Etroeungt Member: 30.5 m bioclastic, tempestitic, marly limestone with crinoids, bryozoans, brachiopods, and ostracods, but lacking calcareous algae and age-diagnostic foraminifers

Discussion: The special importance lies in the local recognition of a HBS to HSS sequence, which provides a correlation with the Sauerland-type succession. Unfortunately, there is so far no record of biostratigraphical markers.

Motorway Junction Langenhorst (Fig. 6)

Location: Exposures created temporarily during the construction of the motorway A44 NW of Velbert (Fig. 9), topographic sheet 4608 Velbert, r 2 572 450, h 5 691 320.

Literature: Michels (1986), Haude and Thomas (1989), Amler et al. (1990), Amler (1993), Brauckmann et al. (1993).

Succession: The outcrop was completely covered or grown over after the end of the roadworks. The lower Tournaisian is locally strongly condensed and probably incomplete.

Pont d’Arcole Formation: (“Zwischenschiefer”):

Beds 81–85, ca. 3 m calcareous, argillaceous siltstone with plant remains and neritic fauna (e.g. with Tylothyris and Brachymetopus germanicus), middle Tournaisian, Lower Alum Shale Event Interval.

Hastière Formation, Laupen Member:

Beds 79–80, upper “oolite-siltstone unit”, ca. 3 m oolites without conodonts, Middle/Upper Crisis Interval to lower Tournaisian.

- ?unconformity (no Hangenberg Black Shale and Hangenberg Shale equivalents) –

Velbert Formation, Etroeungt Member:

Beds 75c–78, lower “oolite-siltstone unit”, first with ca. 2.2 m oolites alternating with micritic limestone and siltstone, then with ca. 1.5 m siltstone; with Bi. ultimus ultimus (Beds 75i, 77b, 78a: “Bi. ziegleri”), Bi. costatus, and Bi. bispathodus (Bi. ultimus ultimus Zone to S. (Eo.) praesulcata s.l. Zone); ?regressive Crisis Prelude.

Beds 65–75b, top part of “sandstone-siltstone unit”, ca. 9.5 m siltstones with a Cyrtoclymenia sp. (Bed 71), phacopids (Omegops sp., Beds 65–75b), Pseudowaribole quaesita (Beds 67, 71–75b), Brachymetopus drevermanni (Beds 71–75b, the oldest species of the genus), Prospira struniana (Bed 71), other neritic fauna, and a thin limestone near the top (Bed 74).

Beds 40–64, upper “sandstone-siltstone unit”, ca. 13.5 m alternating siltstones, thin sandstones, and calcareous sandstones to sandy limestones with neritic fauna including Omegops sp. (?lower part of uppermost Famennian).

Wuppertal area (western Remscheid-Altena Anticline)

B224 outcrops NE of Aprath (Fig. 6)

Location: Temporary outcrops were created during excavations and trenching for the B224 road, which crosses the western part of the narrow Herzkampe Syncline ESE of Wülfrath and NW of Wuppertal-Elberfeld (Fig. 9). A multidisciplinary approach led to a voluminous monograph on the Upper Devonian to Lower Carboniferous (Thomas 1992). The uppermost Devonian und lower Tournaisian were developed as calcareous and micaceous shales and siltstones, which differ from the typical sequence of the Velbert Anticline. The succession, which has no current outcrop, can be summarised as follows (see Korn and Thomas 1988; Thomas 1992; Korn 1992b):

Kahlenberg Formation: Dark-grey to black shale in the upper part of Bed 07, which yielded imprints of smooth-shelled goniatites with up to 15 cm diameter.

Hangenberg Formation equivalent (un-named new formation):

Bed 07, ca. 9 m calcareous siltstones, post-Crisis Interval.

Bed 06/3, 30 cm bioturbated, silty, unfossiliferous limestone.

Stockum Limestone equivalents:

Bed 06/2, 40 cm grey-brown siltstone with abundant Macrobole drewerensis, possibly Upper Crisis Interval III.

Bed 06/1, 20 cm silty shale with pyritised goniatites and micritic limestone concretions with goniatites, such as Ac. (St.) subbilobatum (auct.), Ac. (St.) intermedium (auct.), Ac. (St.) kleinerae, Ac. (Str.) carinatum, and Ac. (Str.) caesari (middle/higher parts of Ac. (St.) prorsum Zone, UD VI-F), probably Upper Crisis Interval II (unfortunately, without conodont record).

Hangenberg Shale:

Beds 05/31–60, 6.5 m grey, calcareous siltstones with partly abundant Guerichia venusta and Pseudowaribole sp., Middle Crisis Interval.

?Hangenberg Black Shale equivalent:

Bed 05/30, marl with large septaria, pyrite accumulations, and a goniatite identified as Acutimitoceras sp. (no conodonts), ?Lower Crisis Interval.

Velbert Formation (s.l.):

Beds 05/21–29, 3.5 m calcareous siltstones with rare oncoids.

Bed 05/20, 70 cm calcareous siltstones with oncoidal rud-/packstones and neritic fauna (brachiopods, gastropods, small solitary Rugosa), ?Crisis Prelude.

Beds 05/2–19, 3.4 m grey, platy, unfossiliferous, calcareous siltstone.

Bed 05/1, 10–20 cm dark grey to black, lenticular, micritic limestone with Pa. gracilis gonioclymeniae (Bi. ultimus ultimus Zone), Rabienops granulatus, and Rab. wedekindi.

Discussion: The regional occurrence of Stockum Limestone was already known to Paeckelmann (1922a, p. 286), who described the DCB section exposed in the railway cut at Kirchenfeld, between Dornap and Aprath (sheet 4708 Elberfeld, ca. r 2 574 500, h 5 681 100). His Bed 9, a dark-grey shale with dark limestone nodules, yielded Macrobole drewerensis and “Brancoceras ornatissimum. Beyond doubt, the latter refers to a species of Ac. (Stockumites) with strong growth ornament. Most interesting is the association with a neritic brachiopod fauna, including productids, spiriferids, chonetids, orthids, and others, which requires revision. A younger, lower Tournaisian gastropod-brachiopod fauna with Syringothyris came from Bed 6, from 4 m below the Lower Alum Shale Event level (Bed 4).

The most westernly occurrences of Stockum Lime-stone, interrupting a succession with few pelagic fossils, underline its transgressive nature. The lower level of large septaria and ammonoids at the B224 may express locally the transgressive Hangenberg Black Shale interval. It is unfortunate that there are no conodont and miospore data and that there are no available outcrops.

Am Haken Brickwork Quarry (Fig. 6)

Location: Former Brickwork Quarry “Am Haken”, second quarry N of the Üllendahl road in Wuppertal-Elberfeld, now completely filled and covered, sheet 4708 Wuppertal-Elberfeld, ca. r 2 580 550, h 5 683 100 (Fig. 9). A second, southern quarry was situated right at the road.

Literature: Paeckelmann (1913: type locality of Platybole bergica; 1922b, 1923, 1928), Schindewolf (1921, 1923b, 1926), Schmidt (1924a, b), Richter and Richter (1926), Paeckelmann (1928), Paul (1938b, 1939a), Basse and Lemke (2011), Zhang et al. (2019). It is the type section of Aganides infracarbonicus Paeckelmann, 1913, a poorly understood prionoceratid. Based on the examination of its types, it was synonymised by Schindewolf (1921) with “Brancoceras Denckmanni Wedekind, 1918” (see Paeckelmann 1922, p. 585, footnote 2), which, however, is another problematic species.

Summary of succession: Paeckelmann (1923, p. 283) gave a relatively detailed log for this unfortunately lost section, which was more fossiliferous and distinctive in terms of lithofacies in comparison to the adjacent Riescheid section. It filled a gap that enabled the westward correlation from the “standard succession” of the northern Sauerland to the Bergisches Land. However, the succession was disturbed by faulting. A modern lithostratigraphic terminology does not exist. The interpretation of Paeckelmann's data leads to the following summary:

Kahlenberg Formation (Lower Alum Shale):

Bed 7, ca. 2 m of alum shale, Lower Alum Shale Event Interval, middle Tournaisian.

Hangenberg Formation equivalent (un-named new formation):

Bed 8, ca. 4 m, dark-grey, Flinz-type limestones (dark turbiditic limestones), in the lower part alternating with shale, post-crisis lower Tournaisian, equivalent of upper part of Hangenberg Limestone.

Bed 9, 3.15 m grey, calcareous shales with thin beds or concretions of partly pyritic, Flinz-type limestone, ?equivalent of lower part of Hangenberg Limestone, post-Crisis Interval, lower Tournaisian.

Near top of Bed 10, black, deeply weathered shale with pyritic “Aganidesinfracarbonicus Paeckelmann, 1913, probably a species of Ac. (Stockumites), and Cymaclymenia sp. (Schindewolf 1921, p. 146), Stockum Level Black Shale, ?Upper Crisis Interval.

Main Bed 10, 3.3 m platy, thin-bedded, bluish-grey shale, with Postclymenia, ?equivalent of Hangenberg Shale, Middle Crisis Interval.

Bed 11, 4.6 m alternating bluish-grey to greenish shales, dark-grey, hard, micaceous shale, and thin-bedded, micaceous fine sandstones and siltstones, with trace fossils (resembling “Nemertites”), Postclymenia and C. striata (Schindewolf 1926, p. 97), probably Lower/Middle Crisis Interval.

“Oberer Cypridinenschiefer” (proposed new Brahm Formation):

Bed 12, 20 cm red marl with squashed clymeniids, possibly Crisis Prelude II.

1 m grey shale with thin sandstones, probably Crisis Prelude I.

20 cm grey and reddish limestone with Richterina and Drevermannia, upper hemisphaerica Zone, pre-Crisis Interval.

4.4 m grey and greenish shale, micaceous shale, and thin sandstones with squashed clymeniids, Guerichia, and Richterina.

Discussion: Most important was a relatively diverse pre-Crisis (“Etroeungt”) fauna with various trilobites (e.g. Rabienops circumspectans), brachiopods, bivalves, crinoids, and bryozoans, which requires revision (outdated species list in Paeckelmann 1913, pp. 137–138), and the recognition of the Postclymenia levels. An adjacent section, again with Postclymenia, was exposed in a brook S of Mirker Hain (sheet 4708 Wuppertal Elberfeld, ca. r 2 579 930, h 5 682 950). Another diverse “Etroeungt” fauna (again with Rab. circumspectans) was collected by H. Schmidt in the former Müller & Preuss Brickwork Quarry, E of the Am Haken Quarry (Paeckelmann 1913, p. 151; trilobites in Richter and Richter 1926). Recent excavations in the Üllendahl region did not reach the DCB (pers. comm. S. Helling).

Riescheid (Fig. 6)

Location: S-N running former railway cut (“Hatzfelder Straßenbahn”) just E of a garden colony in Wuppertal-Wichlinghausen, sheet 4709 Wuppertal-Barmen, sheet 4709 Barmen (Fig. 9), r 2 573 630, h 5 684 520 (GPS N 51° 17′ 15.2″, E7° 11′ 32.4″).

Literature: The long research history started with the work of W. Paeckelmann (1913, 1922a); it has been summarised by Hartenfels et al. (2016).

Summary of succession: For a detailed log see Hartenfels et al. (2016). In the near-absence of macrofauna and conodonts, the DCB stratigraphy is based on the miospore data of Higgs and Streel (1984) and Higgs (in Becker et al. 1993). New palynomorph investigations are under way by C. Hartkopf-Fröder (Krefeld).

Kahlenberg Formation: Ca. 1.2 m dark-grey shale (Beds 91a–91c, Unit 2 of Zimmerle et al. 1980) with very poor macrofauna and miospores of the HD Zone (Higgs and Streel 1984), Lower Alum Shale Event Interval, middle Tournaisian.

- unconformity (no record of the lower Tournaisian VI Zone or Hangenberg Limestone equivalents) -

(proposed) Brahm Formation (previously “Obere Cypridinenschiefer”), Member 4 (Unit 1 of Zimmerle et al. 1980): Ca. 9 m alternating grey, silty shales, and fine- to middle-grained calciturbidites with poor macrofauna (Beds 49b–90):

Within last meter (Samples Rh 02 and Rh 04), “LE Zone”, Middle Crisis Interval.

7 to 1 m below top (Samples Rh 7 to Rh 01 with Verrucosisporites nitidus), LN Zone, Lower/Middle Crisis Interval.

10 m below the top (Sample Rh 10, ca. Bed 82a), LE Zone, pre-Crisis Interval.

15 to 12.5 m below the top (Samples Rh 15 to Rh 12–13, up to ca. Bed 72), LL Zone.

Discussion: Richter and Richter (1926) recorded Weyerites wocklumeriae, a typical uppermost Famennian phacopid, from a dark-grey limestone. Paeckelmann (1923, p. 284) as well as Fuchs and Paeckelmann (1928, p. 38) noted the presence of Postclymenia at Riescheid. This indicates that time equivalents of the Hangenberg Black Shale may be distinguishable in the lower LN Zone interval. The DCB unconformity disqualifies Riescheid as a possible GSSP section but its importance lies in the miospore record, which provides marine-terrestrial correlations.

Northern Sauerland (eastern Remscheid-Altena Anticline)

In the northern Sauerland, between Hagen in the west and Warstein in the east, the “standard” DCB succession (see summary in Becker et al. 2016a) is developed. A major channel fill, the Seiler Conglomerate, forms a short W-E interruption in the Iserlohn area (e.g. Gallwitz 1928; Ziegler 1970; Paproth 1986). The widely used traditional lithological terms do not conform to modern lithostratigraphical standards. The Wocklum Beds or Wocklum Limestone have been based on its distinctive faunas (Wocklumian, UD VI; Schindewolf 1937), not on a sedimentary change that would enable a clear separation from the underlying Dasberg Beds (now Dasberg Formation). Attempts to identify a subordinate marker in the best and continuous sections (Oese, Oberrödinghausen, Effenberg), in order to justify at least a member status, failed so far. In the type section near Wocklum (see below), there is a reddish unit with large kalloclymeniids above a faulted zone. At Oese, a possibly correlative, peculiar interval of red shales and red nodules occurs above the oldest Wocklumian ammonoids. However, we did not trace it in the other sections. Consequently, we continue the use of the term Wocklum Limestone in a traditional, biostratigraphically defined form. The whole interval from the base of the Hangenberg Black Shale to the base of the Lower Alum Shale is assigned to the Hangenberg Formation, which is subdivided into informal members.

Hasselbachtal Auxiliary DCB Stratotype (Figs. 6, 10)

Location: Brook cut of the Hasselbach E in the forest of Hohenlimburg-Reh (Hagen), northern Sauerland, northern limb of Remscheid-Altena Anticline (Fig. 9), topographic sheet Hagen-Hohenlimburg at r 2 507 000/h 5 194 220.

Fig. 10
figure10

DCB succession at the (currently most covered) Hasselbachtal Auxiliary GSSP, showing occurrences of index conodonts and ammonoids, the position of marker bentonites (ω1–3 and a1–3), and their geochronological ages, miospore zones, and changes of carbon isotopes (for references see text, for lithology legend, see Fig. 13)

Literature: Schmidt (1924a, b), Gallwitz (1932: brachiopod records), Paul (1937a: lingulids from the Lower Alum Shale), Groos-Uffenorde and Uffenorde (1974), Paproth and Streel (1982), Becker et al. (1984), Higgs and Streel (1984, 1994), Paproth et al. (1986b), Brauckmann and Hahn (1984), Bless and Groos-Uffenorde (1984), Byvsheva et al. (1984), Becker (1985, 1988, 1996, 2000), Hahn et al. (1990), Kramm et al. (1991), Claoué-Long et al. (1993), Brauckmann et al. (1993), Higgs et al. (1993), House (1993), Korn (1993), Kürschner et al. (1993), Winter (1993), Bless et al. (1993), Becker and Paproth (1993), Becker et al. (1993), Luppold et al. (1994), Higgs and Streel (1994), Sartenaer (1997: type locality of Novaplatirostrum sauerlandese), Korn and Weyer (2003), Trapp et al. (2004), Kaiser (2005), Kaiser et al. (2006), Korn et al. (2010), Feist and Weyer (2018), Korn and Price (2019).

Summary of succession: There were two separate sections along the southern and northern slope of the brook. The southern section is still present and exposes the Wocklum Limestone. Despite protection as a geological heritage, the northern auxiliary stratotype section has been mostly covered by the property owner. Prior to this unfortunate development, the upper Wocklum Limestone was systematically re-sampled in order to improve the ammonoid record. This results in an update of taxon ranges for the northern Wocklum Limestone. The middle Tournaisian to lower Viséan succession was explored in a borehole (Higgs et al. 1993; Luppold et al. 1994) but apart from the miospores it was not studied in the same detail as the outcrop. The following summary combines published and new data. It has a focus on the FODs of stratigraphically relevant taxa.

Hangenberg Limestone: Strongly cyclic succession of grey micritic limestones, nodular and calcareous shales.

Beds 47H–45H with zonally non-diagnostic goniatites, S. (S.) carinthiaca, S. (S.) mehli, Ps. triangulus triangulus, Dinodus sp., and other conodonts (upper S. (S.) mehli Zone).

Bed 48H top, metabentonite a3.

Bed 49H with Pseud. westfalicus (ca. base Pseud. westfalicus Zone, LC I-C), S. (S.) obsoleta, S. (S.) duplicata sensu Hass (= S. (S.) cf. wilberti), Ps. triangulus triangulus, S. (S.) lobata (?M2), and other conodonts (upper S. (S.) mehli Zone).

Bed 51H with Eoc. cf. supradevonicus, Paprothites sp. (top Parag. sphaeroides Subzone, LC I-B2), S. (S.) carinthiaca, S. (S.) bransoni (S. (S.) mehli Zone), and a probably diagenetically triggered negative Ccarb carbon isotope excursion (Kaiser 2005).

Bed 57H with Paragattendorfia sp., Gl. globiforme, H. gracilis, Wey. molaris, and Pap. ruzhencevi (Parag. sphaeroides Subzone, LC I-B2).

Bed 59H with Ac. (St.) convexum, “Mim.hoennense (probably Pap. dorsoplanus Zone, LC I-B1), S. (S.) carinthiaca, S. (S.) duplicata, Ps. triangulus inaequalis, and other conodonts (S. (S.) mehli Zone).

Bed 62H with Wey. reticula.

Bed 63H with S. (S.) cooperi (M2) (base S. (S.) mehli Zone).

Bed 69H with S. (S.) duplicata, Ps. primus ssp., Ps. triangulus inaequalis (base S. (S.) duplicata Zone), and Liobolina cf. submonstrans.

Bed 70H, thin metabentonite a2, dated by Trapp et al. (2004) as 360.2 ± 0.7 ma.

Bed 71H with “Eoc.nodosus and G. subinvoluta (“Eoc.nodosus Subzone, LC I-A3).

Bed 72H with V. peracutus (Eoc.nodosus Subzone, LC I-A3) and S. (Eo.) bransoni (base S. (Eo.) bransoni Zone).

Bed 76H with G. subinvoluta and Ac. (St.) subbilobatum (auct.) (G. subinvoluta Zone/Subzone, LC I-A2).

Bed 78H with Ac. (St.) antecedens (LC I-A2) and Ps. primus ssp. (S. (Eo.) sulcata s.l./Pr. kuehni Zone).

Bed 79H, thin metabentonite a1, first dated by Kramm et al. (1991) and Claoué-Long et al. (1993), revised by Trapp et al. (2004) as 360.5 ± 0.8 ma.

Bed 80H with “G.costata and “Mim.” cf. simile (Korn and Weyer 2003, base G. subinvoluta Zone, LC I-A2); basal post-Crisis Interval.

Upper Stockum Limestone:

Bed 81H with Ac. (St.) intermedium (auct.) (top Ac. (St.) prorsum Zone, LC I-A1), Pr. kockeli, Po. purus purus, Po. purus subplanus, ?Texathyris tarpata, and Macrobole cf. drewerensis.

Bed 83H with Ac. (St.) kleinerae, Ac. (Str.) carinatum (upper Ac. (St.) prorsum Zone, LC I-A1), Po. purus purus, Pr. kockeli, Pr. kuehni, and Belgibole abruptirhachis abruptirhachis.

Bed 84H, bipartite, thin bed with an upper, oolithic, fossiliferous turbidite that eroded an underlying bioturbate, bioclastic wackestone without fauna; with Pr. kockeli, Pr. kuehni, S. (Eo.) sulcata s.l., and numerous reworked Famennian conodonts (base S. (Eo.) sulcata s.l./Pr. kuehni Zone), strong negative excursion of Corg carbon isotopes; base Upper Crisis Interval III.

Stockum Level Black Shale: Bed 85H, 65 cm, solid, dark-grey, calcareous, and pyritic shale with Ac. (St.) subbilobatum (auct.) and Ac. (Stockumites) sp. (including Ac. (St.) cf. prorsum of Becker 1988 and Ac. (Ac) acutum of Korn 1993; middle to top part, Ac. (St.) prorsum Zone, UD VI-F), no conodonts, LN/VI Zone boundary at 14 cm below top (Higgs and Streel 1984) corresponding closely to the Hasselbachtal borehole section (Higgs et al. 1993); Upper Crisis Interval I/II, Lower Stockum Limestone equivalent.

Hangenberg Shale: Bed 86H, ca. 4.85 m of greenish-grey, silty shale with Guerichia (several species), rare squashed Ac. (Stockumites) sp., and a strong positive excursion of Corg carbon isotopes (Kaiser 2005); Middle Crisis Interval.

Hangenberg Black Shale: Bed 115N, 20 cm, transgressive, laminated, and pyritic black shale, with Guerichia and rare Post. cf. evoluta (base Post. evoluta Zone, UD VI-E; base ckI); main Hangenberg Extinction at the sharp base, which was marked by a pyrite seam; base Lower Crisis Interval, base LN Zone (Higgs and Streel 1994).

Wocklum Limestone: Strongly cyclic alternation of greenish, calcareous shales, nodular shales, and grey nodular limestones, intercalated by a few, distinctive metabentonites.

Bed 114N with the last W. denckmanni, P. paradoxa, F. wocklumensis, Liss. wocklumeri, L. similis, C. cf. sudetica, Ebbighausenites seidlitzi (new record), “Mim.geminum (top Epi. applanata Subzone, top UD VI-D2), S. (Eo.) prasesulcata s.l., common Pr. meischneri, Bi. costatus, Br. suprema, Ps. marburgensis trigonicus, Pa. gracilis gracilis, and Pa. gracilis sigmoidalis (top S. (Eo.) praesulcata s.l. Zone), trilobites (Chaunoproetus, Dianops), and small orthids.

Beds 113a-bN with Epi. applanata and Post. nephroides (base Epi. applanata Subzone, base UD VI-D2), base Crisis Prelude.

Bed 109N with the last Pa. gracilis gonioclymeniae (Stoppel in Becker et al. 1984; top of former Middle costatus Zone).

Bed 108N with S. (Eo.) praesulcta s.l., Pr. meischneri, Ps. marburgensis trigonicus, and other conodonts (upper S. (Eo.) praesulcata s.l. Zone), LE Zone (Higgs and Streel 1984).

Bed 107bN with W. denckmanni, P. paradoxa, F. wocklumensis, and Ken. rostratum (new records, W. denckmanni Subzone, UD VI-D1).

Bed 101N with a member of the Cyrto. procera Group (new record).

Bed 92N with W. denckmanni (base W. denckmanni Zone, base UD VI-D1), Pr. meischneri, Bi. ultimus ultimus, and other conodonts.

Bed 87N, metabentonite ω3.

Bed 84N with F. wocklumensis (base May. nucleus Subzone, UD VI-C3).

Bed 82N, metabentonite ω2.

Bed 81N with Ps. marburgensis trigonicus (Kaiser 2005, much delayed FOD in the middle S. (Eo.) praesulcata s.l. Zone) and Pr. meischneri.

Bed 76S top: metabentonite ω1.

Bed 64S with P. paradoxa (base P. paradoxa Subzone, base UD VI-C2).

Bed 46S with M. ?xenostriata (very evolute kosmoclymeniid with rursiradiate ornament, ca. P. paprothae Subzone, UD VI-C1).

Bed 45S with the first Pr. meischneri, Po. vogesi, S. (Eosiphonodella) sp., Bi. ultimus ultimus, Bi. muessenbergensis, Pa. gracilis gonioclymeniae, and other conodonts (higher S. (Eo.) praesulcata s.l. Zone).

Bed 43S with the last Eff. lens and M. ?galeata (ca. top of Eff. lens Zone, top of UD VI-B).

Bed 32S with Eff. lens (base Eff. lens Zone, UD VI-B).

Bed 26S with S. (Eo.) praesulcata s.l. (S. (Eo.) praesulcata s.l. Zone).

Bed 23S with Novaplatirostrum sauerlandense (type level).

Bed 18S with S. (Eo.) praesulcata s.l. and Bi. muessenbergensis (Kürschner et al. 1993, base S. (Eo.) praesulcata s.l. Zone).

Bed 14S with M. bisulcata ssp. and K. cf. undulata (base M. bisulcata Zone, base UD VI-A2).

Bed 12S with M. ?galeata (top L. similis Zone, top UD VI-A1).

Bed 8S with Br. suprema (delayed FOD in the upper Bi. ultimus ultimus Zone).

Bed 4S with K. cf. undulata, R. cf. quadripartitum, and Mim. cf. rotersi (new records, L. similis Zone, UD VI-A1).

Bed 2S with K. subarmata.

Bed 1S with “Mim.geminum, M. sublaevis, Cyrto. plicata, and Cyrto. lateseptata.

Bed 0S with a member of the giant-sized “K.pachydisca Group.

Bed -6S with the locally first Bi. ultimus ultimus (Kaiser 2005; Bi. ultimus ultimus Zone).

Bed -9S with “Mim.” cf. liratum (L. similis Zone, UD VI-A1).

Bed -14S with M. ?sublaevis (L. similis Zone, UDS VI-A1).

Bed -16S with “Mim.liratum (new record, L. similis Zone), Pa. gracilis gonioclymeniae (Bi. ultimus ultimus Zone), and with a possibly diagenetically triggered negative excursion of Ccarbonate carbon isotopes (Kaiser 2005).

Beds -20 to -18S with Muessenbiaergia sp. (new record), Pa. gracilis gonioclymeniae, Bi. bispathodus, and others (Kaiser 2005; Bi. ultimus ultimus Zone).

3 m below Bed 0S, “Mim.liratum (L. similis Zone, basal UD VI-A1).

Discussion: Since the northern and critical DCB part of the outcrop is currently covered, it cannot be considered in the new GSSP search. Attempts to trench a new exposure on lateral public ground was unsuccessful. In addition, Bed 85H, the basal part of the transgressive Crisis Interval III, was not calcareous enough to produce conodont faunas that could shed light on the Pr. collinsoni-Pr. kockeli transition. The thin metabentonites enable a high-precision correlation along the northern limb of the Remscheid-Altena Anticline (Hasselbachtal to Oese and Apricke, Korn and Weyer 2003). So far, only two of them have been dated geochronologically (Trapp et al. 2004: 360.5 ± 0.8 ma for Bed 79H, 360.2 ± 0.7 ma for Bed 70H).

Seiler Trenches N of Iserlohn (Fig. 6)

Location: In 1968, two trenches, Trenches 1 and 2, were dug in the Seiler area N of Iserlohn (sheet 4612 Iserlohn), northern Sauerland (Fig. 9), E of “In der Calle”. The precise location with geographical coordinates is shown in Koch et al. (1970), fig. 1). Subsequently, in 1969 and 1970, five additional trenches, Trenches 0 to III, and a “Paralleltrench”, were excavated in the a-b-parts of Trench 2, which positions are shown in Clausen et al. (1989a, fig. 15). All trenches were filled and currently there are only minor exposures at “In der Calle”, which yield loose blocks of the famous Seiler Conglomerate.

Literature: Schmidt (1924a, b), Schindewolf (1926), Richter and Richter (1926), Gallwitz (1928, 1932), Matern (1929), Rabien (1954, 1960), Koch et al. (1970: type locality of Pr. kuehni, Po. stadleri, Richterina (Fossirichterina) intercostata serratocostata, Maternella (M.) circumcostatula, M. (M.) gruendeli, and M. (Zagoruendella) seilerensis), Paproth and Streel (1982), Clausen et al. (1989a).

Summary of succession: The Seiler area exposed a unique, thick oolite-sandstone-shale succession in the DCB interval, the Seiler Channel (Paproth et al. 1986a, b). Partly, it corresponds to an incised valley fill formed after the main Hangenberg Regression (sequence boundary), which is the proximal equivalent of the Hangenberg Sandstone. However, conodonts proved that the overall succession is much more complex, with siliciclastic sedimentation starting much earlier in the uppermost Famennian. The source of the material must have been on a topographic high to the N (Koltonik et al. 2018), not on a Rhenish Island in the S, as proposed in former palaeogeographic reconstructions. The combined evidence from Gallwitz (1928), Koch et al. (1970), and Clausen et al. (1989a) leads to the following DCB summary:

Kahlenberg Formation (Lower Alum Shale): 25 m black shale, middle Tournaisian.

Hangenberg Limestone:

Trench 2, 25.0–33.9 m, olive-grey, partly micaceous shale, at the base with Richterina (R.) latior, Maternella (M.) circumcostatula, M. (Zagoruendella) seilerensis, and other ostracods (Samples 7a/7b), R. (R.) latior Zone, top lower Tournaisian.

Trench 2, Samples 10–8, Section III, Bed 9, Section II, Bed 17, Section I, Bed 14, and Section 0, Bed 11 with S. (S.) lobata M1, S. (S.) obsoleta, S. (S.) sandbergi, S. (S.) quadruplicata, and Ps. triangulus triangulus (S. (S.) lobata M1 Subzone).

Section III, Bed 8, Section II, Bed 16, and ?Section 0, Beds 9–10 with S. (S.) quadruplicata, S. (Eo.) isosticha (?cf.), and S. (S.) obsoleta (S. (S.) sandbergi Zone/Subzone).

Marker Bentonite 2.

Trench 2, Sample 12, Section II, Bed 15, Section I, Beds 11–13, Section 0, Beds 7–8 with S. (S.) obsoleta, S. (S.) quadruplicata, S. (S.) mehli, S. (S.) cooperi, and Ps. triangulus triangulus (upper part of S. (S.) mehli Zone).

Trench 2, Sample 13, Section III, Bed 7, Section II, Beds 13–14, Section I, Beds 9–10, and Section 0, Beds 4–6 with S. (S.) mehli, S. (S.) carinthiaca, S. (S.) cooperi, “S. duplicata sensu Hass” (= S. (S.) cf. wilberti), S. (S.) quadruplicata (?M2), and Ps. triangulus triangulus (lower S. (S.) mehli Zone).

Trench 2, Sample 14, Section III, Bed 6 with Ps. triangulus triangulus, first S. (S.) quadruplicata (?M2), and S. (S.) duplicata (top S. (S.) duplicata or basal S. (S.) mehli Zone).

Trench 2, Sample 15 (type level of Pr. kuehni), Section III, Beds 4–5, Section II, Beds 11–12, Section I, Bed 8, and Section 0, Bed 3 with S. (S.) duplicata, S. (S.) bransoni, and Ps. triangulus inaequalis (S. (S.) duplicata Zone).

Section II, Bed 10 with S. (S.) bransoni and S. (Eo.) sulcata s.l. (S. (S.) bransoni Zone).

Section I, Bed 7 and Section 0, Bed 2 with S. (Eo.) sulcata s.l., Pr. kuehni, Pr. kockeli, Po. purus subplanus, and Ps. dentilineatus (upper S. (Eo.) sulcata s.l./Pr. kuehni Zone), basal post-Crisis Interval.

Shale with Marker Bentonite 3 and a few conodont-poor limestone nodules below (Section II, Bed 9).

Stockum Limestone:

Trench 2, Sample 16, Trench 2b, Samples II 23–21, “Paralleltrench”, Beds 1–3, Section III, Bed 3, Section II, Beds 7–8, and Section I, Beds 5–6 with Pr. kuehni, Pr. kockeli, Ps. dentilineatus, rare S. (Eo.) sulcata s.l., Po. purus purus, and Po. purus subplanus (lower S. (Eo.) sulcata s.l./Pr. kuehni Zone), Upper Stockum Limestone, Upper Crisis Interval III.

Trench 2, Samples 18–17, Section III, Beds 1–2, Section II, Bed 6, Section I, Beds 3–4, Section 0, Bed 1 with Pr. kockeli, Pr. collinsoni, and Pr. meischneri (Pr. kockeli Zone), Lower Stockum Limestone, Upper Crisis Interval II.

Section II, Beds 1–5, Section I, Beds 1–2, and Section 0, Bed 0 with Pr. collinsoni, Pr. meischneri, Neo. communis ssp., and many reworked taxa (in Section I, upper costatus-kockeli Interregnum), Basal Stockum Limestone, Upper Crisis Interval I.

Seiler Formation, Upper Member (equivalents of Hangenberg Shale/Sandstone):

Trench 2, 37.4–54.6 m, olive-grey, silty shales alternating with thin, micaceous sandstones, top Middle Crisis Interval II.

Trench 2, 54.6–73.5 m, two packages of micaceous sandstone, in the lower part up to 15 cm thick beds, interrupted by a ca. 4 m thick silty shale interval.

Trench 2, 73.5–96.5 m, olive-grey silty shales and thin, micaceous sandstones.

Trench 2, 95.5–135,0 m, dark-grey to olive-grey, partly silty shales, with some calcareous concretions at 110.0–115.0 m and a 20 cm thick, micaceous and calcareous sandstone at ca. 128 m.

Trench 2, 135.0–152.2 m, dark-grey, solid, fine to coarse, micaceous sandstones, and conglomerates with quartz pebbles up to 3 cm in diameter.

Trench 2, 152.2–172 m, banded, olive-grey to dark-grey, partly silty and micaceous shale.

Trench 2, 172.0–203.8 m, predominant dark-grey, micaceous, fine- to middle-grained, partly conglomeratic sandstones and some intercalated, olive-grey, silty shales.

Trench 2, 203.8–225.0 m, fine to conglomeratic sandstones, partly with abundant ooids, and some packages of olive-grey, silty, micaceous shale, base Middle Crisis Interval II.

Trench 2, 225.0–227.0 m, greenish-grey, silty, micaceous shale.

Trench 2, 227.0–228.0 m, oolite with some reworked pebbles of black limestone, base Middle Crisis Interval I; this is probably the level of Postclymenia found by Gallwitz (1928, p. 498) in oolite and in association with spiriferids, productids (productines and chonetines), and pectinids.

Hangenberg Black Shale equivalent:

Trench 2, 228.0–228.3 m, black, detrital limestone with bivalves, unfortunately, not sampled for conodonts, Lower Crisis Interval, upper part.

Trench 2, 228.3–229.5 m, dark-grey, micaceous shale, Lower Crisis Interval, lower part.

Seiler Formation, Middle Member (Wocklum Limestone time equivalents):

Trench 2, 229.5–230.0 m, light-grey, thin-bedded, micritic limestone with Pa. gracilis gracilis, Bi. aculeatus aculeatus, and Bi. spinulicostatus (Sample 51, probably top S. (Eo.) praesulcata s.l. Zone), Crisis Prelude.

- ca. 7.5 m gap -

Trench 2, 237.5–240.0 m, dark-grey, platy marl and dark- to olive-grey, slightly micaceous shale with Maternella (M.) hemisphaerica, M. (M.) dichotoma, M. (M.) gruendeli, and R. (Fossirichterina) intercostata serratocostata (Samples 53/52, M. (M.) hemisphaerica-M. (M.) dichotoma Zone), pre-Crisis Interval.

Trench 2, 240.0–241.5 m, bluish-grey, thin-bedded, detrital limestone with fragmented brachiopods and bivalves, Pa. gracilis gracilis, Pa. gracilis sigmoidalis, reworked Pa. perlobata ssp., Ps. marburgensis trigonicus, Bi. costatus, and other conodonts (Sample 54, Bi. ultimus ultimus Zone).

Trench 2, 241.5–251.5 m, grey, fine- to middle-grained, calcareous and micaceous sandstones, partly conglomeratic and olive-grey, silty shales in the upper part.

Trench 2, 251.8–252.6 m, sandy limestone conglomerate, clasts up to 3 cm, with Pa. gracilis gonioclymeniae, Ps. marburgensis trigonicus, and reworked middle Famennian palmatolepids (Sample 56, Bi. ultimus ultimus Zone).

Trench 2, 252.6–266.0 m, grey, fine- to middle-grained, micaceous sandstones and shale interbeds.

Trench 2, 266.0–266.4 m, coarse, light-grey limestone conglomerate with calcareous matrix, Pa. gracilis gonioclymeniae, Bi. costatus costatus, and many reworked lower/middle Famennian conodonts (Sample 57, basal Bi. ultimus ultimus Zone).

Discussion: Conodont faunas from the post-Crisis Hangen-berg Limestone of the Seiler are most important to understand the Rhenish lower Tournaisian siphonodellid succession. Therefore, it is very unfortunate that no re-sampling is currently possible. Another interesting feature is the brief report of a detrital black limestone at the base of the Crisis Interval, which, unfortunately, was not studied in detail. It may represent one of the globally rare limestones deposited during the main anoxic pulse.

In Trench 1 the pre-Crisis uppermost Famennian lacked the sandstones and conglomerates of Trench 2 and was rich in dark-grey platy limestones with conodonts. The Seiler Channel was characterised by a small-scale palaeotopography and fast lateral facies changes. Gallwitz (1928, p. 497) listed a Wocklumian ammonoid fauna with K. subarmata, Mimimitoceras (= “Aganides? quadripartitus”) and Linguaclymenia/Muessenbiaergia (“Oxyclymenia bisulcata”).

Oese (Figs. 6, 11)

Location: Northern slope of road cut of the B7 near Hemer-Oese, northern Sauerland (Fig. 9), topographic sheets 4612 Iserlohn to 4512 Menden, central point at r 3 415 640/h 5 696 900.

Fig. 11
figure11

Summary section log for the DCB succession at Oese (B7 roadcut), showing selected occurrences of index ammonoids, conodonts, and marker bentonites in relation to the numberings of Ziegler (1971: Hangenberg Limestone, A-S numbers), Becker et al. (1993: packages of Wocklum Limestone), Korn and Weyer (2003: Hangenberg Limestone, nos. 1–38), Nowak (2008: Wocklum Limestone to Hangenberg Shale, nos. 174c–229), and Kaiser et al. (2017: Hangenberg Limestone, Kai numbers). For abbreviated zones and lithological units, see Fig. 1; for references to the numerous records, see text,* = reworked; for lithology legend, see Fig. 13

Literature: Schmidt (1924a, b), Ziegler (1962, 1971), Conil and Paproth (1968), Streel (1969), Paproth and Streel (1970, 1982), Henningsen (1972), Groos-Uffenorde and Uffenorde (1974), Stoppel 1977, Korn (1981a), Higgs and Streel (1984), Keupp and Kompa (1984), Paproth et al. (1986b), Struve (1989: type locality of Rabienops evae), Kürschner et al. (1993), Becker et al. (1993), Luppold et al. (1994), Becker (1996, 2000), Korn and Weyer (2003), Kaiser (2005), Bomfleur (2005), Nowak (2008), Hartenfels (2011), Kaiser et al. (2017), Korn and Price (2019).

Summary of succession: Although the section has been studied by numerous authors, there is no published bed-bed-bed fossil account for the complete Wocklum Limestone. Uppermost Famennian ammonoids have not been collected with the same precision as at adjacent sections (e.g. Becker et al. 1993). The uppermost Famennian summary is based on Luppold et al. (1994), Korn (2002), and Nowak (2008), with still preliminary conodont data. For the lower Tournaisian, there are several logs (e.g. Ziegler 1971; Luppold et al. 1994; Korn 2002; Kaiser 2005), partly with different bed numbers, which are synthesised here:

Kahlenberg Formation (Lower Alum Shale): Laminated, unfossiliferous black alum shale with a lenticular, laminated, siliceous, massive limestone (no conodonts) in the lower part (first depicted by Paproth and Streel 1982).

Hangenberg Limestone: Ca. 1.5 m of cyclic, bioturbated, grey, solid cephalopod limestone (bioclastic wackestone), nodular limestone, nodular shale, and calcareous shale; macrofauna in specific beds (Kullmann in Paproth and Streel 1982, Kullmann in Becker et al. 1993; Korn and Weyer 2003):

Korn-Bed 37(c), nodule layer with Eoc. cf. supradevonicus (higher part of Parag. patens Zone, LC I-D).

Korn-Bed 36 (Bed S), massive limestone, radiolarian wackestone, with Eoc. supradevonicus (ca. base Parag. patens Zone, LC I-D).

Korn-Bed 35 (Kaiser-Bed 23), 30 cm tuffitic clay bed, probably metabentonite a3 (high in the S. (S.) mehli and Pseud. westfalicus Zones at Hasselbachtal).

Korn-Bed 33 (Bed R, Kaiser-Bed 22b), nodule layer with Nic. cf. trochiforme and S. (S.) obsoleta (upper part of S. (S.) mehli Zone).

Korn-Bed 31 (Bed Q, Kaiser-Bed 21), solid limestone with S. (S.) cf. wilberti, S. (S.) carinthiaca (Fig. 2o), and S. (S.) lobata M1 (S. (S.) mehli Zone).

Korn-Bed 30 (upper part of Kaiser-Bed 20), nodule layer with Kaz. evoluta, Pseudarietites sp., and Wey. molaris (upper part of Pseud. westfalicus Zone).

Korn-Bed 28 (lower part of Kaiser-Bed 20), nodule layer with Pseud. westfalicus, Pseud. cf. subtilis, Gl. globiforme, Paragattendorfia n. sp. I, Wey. molaris, and “Wey.concava (base Pseud. westfalicus Zone, LC I-C).

Korn-Bed 25 (Bed N, Kaiser-Bed 18), nodular limestone with Pap. dorsoplanus and other goniatites (upper Pap. dorsoplanus Zone, LC I-B2).

Korn-Bed 23 (Bed M, Kaiser-Bed 17), nodular limestone with S. (S.) obsoleta, S. (S.) carinthiaca, S. (S.) belkai M1 (S. (S.) mehli Zone), and other conodonts; base of the “triangulus triangulus Zone” after Ziegler (1971).

Korn-Bed 22, upper part (Kaiser-Bed 16), nodular limestone with Pap. dorsoplanus, Paragattendorfia n. sp. I and II (Parag. sphaeroides Subzone, LC I-B2).

Korn-Bed 20 (Bed K, Kaiser-Bed 14) with S. (S.) duplicata, S. (S.) duplicata sensu Hass (= S. (S.) cf. wilberti), an intermediate between S. (S.) duplicata and S. (S.) cooperi, S. (Eo.) sulcata s.l., Ps. triangulus inaequalis, and other conodonts, including many problematical juvenile siphonodellids (?basal S. (S.) mehli Zone).

Korn-Bed 19 (Bed J, Kaiser-Bed 13), solid limestone with S. (S.) duplicata, Ps. triangulus inaequalis, and an atypical S. (S.) cooperi (S. (S.) duplicata Zone).

Korn-Bed 15 (Bed G, Kaiser-Bed 11) with “Mim.varicosum.

Korn-Bed 14, upper part, thin metabentonite a2 (upper part of S. (Eo.) bransoni Zone at Hasselbachtal).

Korn-Bed 13 (lower part of Kaiser-Bed 10), nodule layer with abundant Pr. kockeli and S. (Eo.) sulcata s.l., base of the “triangulus ineaqualis Zone” according to Ziegler (1971).

Korn-Bed 12 (Bed F, Kaiser-Bed 9), solid limestone with S. (Eo.) bransoni (base S. (Eo.) bransoni Zone).

Korn-Bed 9 (Bed D, Kaiser-Bed 7), nodular limestone with Ps. multistriatus.

Korn-Bed 6 (Bed C, Kaiser-Bed 5), solid limestone with S. (Eo.) sulcata s.l., S. (Eo.) praesulcata s.l., Ps. primus ssp., and Po. purus subplanus (S. (Eo.) sulcata s.l./Pr. kuehni Zone); basal post-Crisis Interval.

Stockum Limestone equivalents:

Korn-Bed 4 (lower part of B, Kaiser-Bed 4b), nodular limestone with Pr. kuehni (Fig. 2i), Pr. kockeli, S. (Eo.) sulcata s.l., Po. purus purus, and Clydagnathus plumulus (base S. (Eo.) sulcata s.l./Pr. kuehni Zone), Upper Stockum Limestone; Upper Crisis Interval III.

Korn-Beds 2–3 (Kaiser-Bed 4a), nodular limestone and subsequent nodule layer with Pr. meischneri, Lower Stockum Limestone; Upper Crisis Interval II.

Korn-Bed 1 (Bed A, Kaiser-Bed 3), laminated, graded, micaceous, silty, turbiditic limestone with Pr. kockeli (Kürschner et al. 1993; Luppold et al. 1994), and reworked Bi. bispathodus and Pa. gracilis gracilis (Pr. kockeli Zone); Upper Crisis Interval II.

Hangenberg Sandstone: 12–14 m micaceous, siliceous and calcareous, fine sandstone in partly massive beds with ripple cross-bedding, flaser bedding, mudclasts at the base, channels, and plant debris (for sedimentology see Keupp and Kompa 1984), LN Zone in the upper part; Middle Crisis Interval II. The base is currently not exposed. The provenance of the sand is from the north (Koltonik et al. 2018), not from a shoal in the southernly core of the Remscheid-Altena Anticline (Paproth et al. 1986a).

Hangenberg Shale: 10–15 m thin-bedded, silty, greenish-grey, calcareous shale, which is rich in miospores (Higgs and Streel 1984); Middle Crisis Interval I.

Hangenberg Black Shale: Ca. 15 cm laminated, black shale with common Post. cf. evoluta (Fig. 3k; Post. evoluta Zone, UD VI-E, 15 cm), with sharp base, and grading upwards into ca. 15 cm silty, dark-grey shale; main Hangenberg Extinction at the base, Lower Crisis Interval.

Wocklum Limestone: Strongly cyclic, fossiliferous alternation of solid nodular limestone, nodular shale, and mostly greenish (exceptionally reddish), silty, calcareous shale. The logs in Luppold et al. (1994, with numbers) and Korn (2002, without numbers, = Korn and Weyer 2003) do not match well.

Upper 35 cm (Korn-Beds 1–2, Becker-package 1, Nowak-Beds 226a–227c) with W. denckmanni (Nowak-Beds 226e, 227b, 227c), P. paradoxa (Nowak-Beds 226b, 226d, 226e), F. wocklumensis (cf. Nowak-Bed 226d), Liss. wocklumeri (Nowak-Beds 226d, 227b), C. striata (Nowak-Bed 226d), C. ?involvens (Nowak-Bed 227b), C. cf. sudetica (Nowak-Bed 226d), Cyrtoclymenia n. sp. (Nowak-Bed 227a), “Mim.geminum (Becker-package 1), “Mim.” cf. liratum, Sp. orbiculare ssp., Ken. rostratum, May. nucleus (Nowak-Bed 227b) (W. denckmanni Zone, UD VI-D), Bi. ultimus ultimus (reported as Bi. ziegleri ziegleri in Luppold et al. 1994), Bi. costatus, Ps. marburgensis trigonicus, Pa. gracilis (three subspecies), Br. suprema, and Po. obtectus (top of S. (Eo.) praesulcata s.l. Zone), pre-Crisis Intervall and Crisis Prelude.

Ca. 80 cm nodular limestone and shale (Becker-package 2, Korn-Beds 3–6, Nowak-Beds 213b–225b) with two more solid limestones (Nowak-Beds 233b, 224b), P. paradoxa (Nowak-Beds cf. 213a, cf. 217b, 224b), L. wocklumeri (Nowak-Beds 218b, 224b, 225b), Gl. glaucopis (Nowak-Bed 224b), Finiclymenia sp. (Nowak-Bed 225b), C. striata (Nowak-Beds 218b, cf. 225b), Protactoclymenia n. sp. (Nowak-Bed 225b), Sp. muensteri orbiculare (ca. Nowak-Bed 223b), May. sinuconstrictum (loose specimen, Figs. 3g–h), R. lineare (Nowak-Bed 225b), and R. quadripartitum (Nowak-Bed 225b) (P. paradoxa to May. nucleus Subzones, UD VI-C2/3), with the first Pr. meischneri in Bed 6 and the last Pa. gracilis gonioclymeniae in Bed 5 of Kaiser (2005).

12 cm calcareous shale (Becker-package 3, between Korn-Beds 6 and 7, Nowak-Beds 212a-213a), with bentonite ω1 (within P. paradoxa Subzone, UD VI-C2, at Hasselbachtal).

78 cm nodular limestone and shale (upper part of Becker-package 4, Korn-Beds 7 to > 10, Nowak-Beds 202b-211b) with Eff. minutula (e.g. Nowak-Bed 210j), Mim. trizonatum (Nowak-Bed 210b), Gl. glaucopis (Nowak-Bed 210l), C. striata (e.g. Nowak-Bed 205a), C. costellata (Eff. lens Zone to P. paprothae Subzone, UD VI-B to VI-C1), and S. (Eo.) praesulcata s.l. (Kaiser 2005; S. (Eo.) praesulcata s.l. Zone).

Ca. 40 cm shale (lower third of Becker-package 4, Nowak-Beds 199c–202a) with three nodular limestone beds (Nowak-Beds 199c, 200d, 201b) and two nodule layers, Muessenbiaergia sp. (Nowak-Bed 202a) and K. subarmata (Nowak-Bed 200a) (M. bisulcata Zone, UD VI-A2).

Ca. 40 cm reddish marker interval (Becker-package 5, Nowak-Beds 195a–199c) with M. cf. bisulcata, K. pessoides, K. subarmata, L. similis, C. involvens, C. costellata, “Mim.geminum, “Mim. liratum”, R. quadripartitum, and other goniatites (M. bisulcata Zone, UD VI-A2).

Ca. 45 cm nodular limestone and shale (Becker-package 6, Nowak-Beds 188d–194c).

Ca. 30 cm greenish-grey, silty shale (Becker-package 7, Nowak-Beds 188a–c) with rare limestone nodules (Nowak-Bed 188b).

46 cm nodular shale and three beds of nodular limestones in the upper part (Becker-package 8, Nowak-Beds 183b–187b) with R. quadripartitum (probably L. similis Zone, UD VI-A1), the oldest S. (Eo.) praesulcata s.l. in the upper part (Nowak 2008, Bed 187b, base S. (Eo.) praesulcata s.l. Zone) and Pa. gracilis gonioclymeniae at the base (upper Bi. ultimus ultimus Zone).

55–60 cm reddish nodular limestone, nodular shale, and shale (Becker-package 9, Nowak-Beds 178d–183a) with Ps. marburgensis trigonicus and Bi. ultimus ultimus (Nowak-Bed 180b, lower Bi. ultimus ultimus Zone), basal Wocklum Limestone.

50 cm greenish-grey, silty shale (Nowak-Beds 178a–c), “Strunian Transgression”.

Discussion: The thin beds of the kockeli Zone are, unfortunately, locally rather poor in conodonts and devoid of ammonoids. This diminishes the DCB potential of the section. The shale package at the base could be used for a lithostratigraphic distinction of the overlying Wocklum Limestone but has not yet been correlated with the Oberrödinghausen section. The lower reddish interval (Nowak-Beds 178d–183a) may correlate with a distinctive reddish unit at Wocklum that yielded large-sized Kalloclymenia.

Apricke (Fig. 6)

Location: Small gully ca. 1 km N of Apricke, topographic sheet Iserlohn, near eastern end of Remscheid-Altena Anticline (Fig. 9), r 17 690/h 96 250.

Literature: Schmidt (1924a, b), Richter and Richter (1926: type locality of Cyrtosymbole nepia and Phacops wedekindi), Matern (1929), Paul (1939b), Korn (1981a), Paproth and Streel (1982), Higgs and Streel (1984), Paproth et al. (1986b), Korn and Price (1987), Luppold et al. (1994), Feist et al. (2000: type locality of Haasia aprickensis, Anglibole archinalae, and Struveproetus ocellatus), Becker (2000), Korn and Weyer (2003), Korn and Price (2019).

Summary of succession: The section logs and descrip-tion in Luppold et al. (1994) and Korn and Weyer (2003), unfortunately, have a different bed numbering and differ, especially for the Wocklum Limestone nodule layers. For the Stockum/Hangenberg Limestones, we give preference to the more detailed 2003 numbering, but adding an H (1994 numbers in brackets), in order to enable a clear distinction from the partly identical Wocklum Limestone numbers.

Kahlenberg Formation (Lower Alum Shale): ca. 1.5 m black shale.

Hangenberg Limestone: 2 m cyclic alternation of solid or nodular, poorly fossiliferous limestone and calcareous shale, followed by a 1.7 m thick grey shale unit (Beds 11–15).

Bed 34H (16) with S. (S.) lobata (M2?), S. (S.) obsoleta, Ps. pinnatus, and Ps. triangulus triangulus (upper part of S. (S.) sandbergi Zone).

Bed 29H (upper part of 22), thin metabentonite a3 (upper part of S. (S.) mehli Zone).

Bed 25H (25) with S. (S.) lobata (M2?) and “S. duplicata” s.l. (S. (S.) mehli Zone).

Bed 15H (within 32), thin metabentonite a2 (upper part of S. (Eo.) bransoni Zone).

Beds 13H/14H (33) with “S. duplicata” s.l. (S. (Eo.) bransoni Zone).

Bed 8H (between 36 and 35), thin metabentonite a1 (see position above the first gattendorfiid at Hasselbachtal).

Stockum Limestone equivalents:

Bed 6H (36) with S. (Eo.) sulcata s.l., Pr. kockeli, and Po. purus purus (S. (Eo.) sulcata s.l./Pr. kuehni Zone); Upper Stockum Limestone, Upper Crisis Interval III.

Bed 5H (37), thin turbiditic limestone with Pr. kockeli and the normally rare Po. biconstrictus; possibly Upper Crisis Interval III.

Bed 4H, very thin turbiditic limestone, onset of a minor DCB regression.

Bed 2H, nodular limestone with Ac. (Str.) cf. carinatum, Ac. (Stockumites) sp. (upper Ac. (St.) prorsum Zone), and Pr. kockeli (Lower Stockum Limestone).

Bed 1H, thin, solid, laminated, turbiditic limestone with numerous small-sized goniatites, Po. purus purus and Ps. primus ssp. (Pr. kockeli Zone), Upper Crisis Interval II.

Hangenberg Shale: Bed 41, ca. 4.8 m greenish-grey shale, more silty towards the top, middle ckI, upper part with LN Zone; Middle Crisis Interval.

Hangenberg Black Shale: Bed 42, 15–20 cm black shale with Post. cf. evoluta (C. euryomphala in Paproth and Streel 1982), lower ckI, Lower Crisis Interval; main Hangenberg Extinction at the base.

Wocklum Limestone: Cyclic alternation of fossiliferous, solid cephalopod limestone, nodular limestone, nodular shale, and calcareous shale.

Bed 1, five layers of limestone nodules with Wocklumeria and other ammonoids (W. denckmanni Zone, UD VI-D), and the last Bi. ultimus ultimus (recorded as Bi. ziegleri ziegleri), Bi. muessenbergensis, Br. suprema, Pa. gracilis gracilis, Pa. gracilis sigmoidalis, and Ps. marburgensis trigonicus (top S. (Eo.) praesulcata s.l. Zone), type level of Haasia aprickensis, Anglibole archinalae, and Struveproetus ocellatus, Crisis Prelude.

Bed 3, five layers of limestone nodules with Wocklumeria (W. denckmanni Zone, UD VI-D), pre-Crisis Interval.

Bed 4, bipartite solid flaser limestone (?top P. paradoxa Zone (UD VI-C), with Bi. ultimus ultimus and Pa. gracilis gonioclymeniae (S. (Eo.) praesulcata s.l. Zone by ammonoid correlation).

Bed 7, lower part, metabentonite ω3 (within May. nucleus Subzone, UD VI-C3, see position of ω3 at Hasselbachtal).

Bed 8 with the P. paradoxa Zone (UD VI-C).

Discussion: Beds 1H–6H (39–36) should be re-sampled for conodonts in order to find a Protognathodus succession. Korn and Weyer (2003) proposed to correlate the turbiditic Bed 1H with the turbiditic Bed 84H at Hasselbachtachtal. If this is correct, Beds 2H–6H at Apricke correlate with the Upper Stockum Limestone interval (Beds 83H–81H) at Hasselbachtal, which is supported by the overlying thin metabentonite a1 in both sections. However, it is also possible that the thin Hasselbachtal turbidite (Bed 84H) correlates with the upper thin turbidites at Apricke (Beds 4H/5H).

Oberrödinghausen Railway Cut (Figs. 7, 12)

Location: This is the original DCB stratotype section selected in 1935. It lies at the eastern slope of railway cut near Oberrödinghausen, eastern end of Remscheid-Altena Anticline (Fig. 9), topographic sheet 4613 Balve, r 3 419 400/h 5 696 100. An adjacent section (type locality of K. (K.) schindewolfi Korn and Price, 1987) was formerly exposed on the eastern slope of the road cut in Oberrödinghausen (see section logs in Ziegler 1962 and Luppold et al. 1994, p. 22). In addition, the DCB was encountered in the Oberrödinghausen 1 borehole (e.g. Higgs and Streel 1984; Van Steenwinkel 1984).

Fig. 12
figure12

Summary section log for the DCB succession in the Oberrödinghausen Railway Cut (Hönne Valley), showing selected occurrences of index ammonoids, conodonts, and marker bentonites. Bed numberings after Schindewolf (1937: Wocklum Limestone, nos 23–1), Voges (1959, 1960: Hangenberg Limestone samples, Vo numbers), Vöhringer (1960: Hangenberg Limestone, nos. 6–1), Ziegler (1971: Hangenberg Limestone, Zi numbers), Korn and Weyer (2003: Hangenberg Limestone, some subdivision of Vöhringer numbers), and Sacher (2016: Wocklum Limestone to basal Hangenberg Limestone, nos. 178b–234b). For abbreviated zones and lithological units, see Fig. 1; for references to the numerous records, see text, * = reworked; for lithology legends, see Fig. 13

Literature: Schmidt (1924a, b), Paeckelmann (1924), Richter and Richter (1926: type locality of Perliproetus gradatus and Weyerites wocklumeriae; 1951), Matern (1929), Schindewolf (1926): type locality of Eoc. supradevonicus, Eoc. spiratissimus, and “Eoc.planus; 1937: type locality of W. plana, W. aperta, Postglatziella carinata, Kamp. endogona, Kamp. trigona, and Triaclymenia triangularis), Paeckelmann and Schindewolf (1937), Paul (1937b, 1939b), Paeckelmann and Kühne (1938), Rabien (1954), Bischoff (1957), Voges (1959, 1960), Vöhringer (1960: type locality of N. trochiforme, N. subacre, N. acre, “Mim.exile, “Mim.simile, Ac. (St.) depressum, Ac. (St.) undulatum, Ac. (St.) convexum, Ac. (St.) antecedens, Ac. (Str.) heterolobatum, H. multisulcata, H. gracilis, H. sphaeroidalis, Gl. globiforme, Parag. patens, Cost. ornatum, “Gatt.costata, “Gatt.reticulum, Wey. concava, “Wey.” molaris, Kazakhstania evoluta, Pap. raricostatus, Pseud. subtilis, Pseud. planissimus, Pseud. serratus, V. peracutus, Eoc. brevis, and “Eoc.tener), Ziegler (1962: type locality of Spathognathodus supremus, Spath. werneri, Ps. trigonica, Ps. brevipennata, Po. vogesi, Po. obliquicostata, and Pa. deflectens sigmoidalis; 1971), Streel (1969), Paproth and Streel (1970), Eickhoff (1973), Stoppel 1977, Korn (1981a, 1992a, 2006), Paproth and Streel (1982), Brauckmann and Hahn (1984), Ziegler and Sandberg (1984b), Higgs and Streel (1984, 1994), Van Steenwinkel (1984), Korn and Price (1987), Korn and Luppold (1987), Price and Korn (1989), Kürschner et al. (1993), Brauckmann et al. (1993), House (1993), Luppold et al. (1994), Becker (1996, 1997, 2000, 2002), Crônier and Feist (2000), Korn and Weyer (2003), Korn and Vöhringer (2004), Kaiser (2005), Ebbighausen and Korn (2007), Clausen and Korn (2008), Becker et al. (2016a), Korn et al. (2016), Sacher et al. (2016), Sacher et al. (2016), Kaiser et al. (2017), Feist and Weyer (2018), Mottequin et al. (2019), Korn and Price (2019).

Summary of succession: The section is extremely useful for ammonoid-conodont correlation but the conodont record for the uppermost Famennian is still incomplete (Sacher 2016; Sacher et al. 2016). The Famennian part has been logged at much higher resolution than before by M. Sacher and S. Hartenfels (Sacher-beds). In the lower Tournaisian, the detailed conodont data of Ziegler (1971) have never been published. Therefore, the combined data of Voges (1959) and Kaiser et al. (2017) form the main account for the Carboniferous conodonts. The ammonoid record is mostly from Schindewolf (1937) and Vöhringer (1960), but with various subsequent updates (e.g. Luppold et al. 1994; Becker 2000; Korn 2006; Becker et al. 2016a). The summary focuses on the FODs and LODs of taxa:

Kahlenberg Formation (Lower Alum Shale): More than 15 m black shale with miospores of the HD Zone at the base (Higgs and Streel 1984), in the middle with phosphorite no-dules, and then gradually siliceous (Becker et al. 1993).

Hangenberg Limestone: 1.5 m alternating, fossiliferous flaserlimestone, nodular limestone, nodular shale, and grey shale.

Bed 1a (Ziegler-Bed 17, Voges-Sample 11), ca. 12 cm limestone with S. (S.) lobata M1, Po. radinus, and Dinodus leptus (upper part of S. (S.) sandbergi Zone = S. (S.) lobata M1 Subzone).

Bed 1b (Ziegler-Bed 16, Voges-Sample 10), ca. 12 cm solid limestone with Pseud. serratus, Eoc. planus (upper Parag. patens Zone, LC I-D), S. (Eo.) cf. isosticha, and S. (S.) quadruplicata (Fig. 2t) (higher S. (S.) sandbergi Subzone).

Beds 2a–2b (Ziegler-Beds 14–15, Voges-Sample 9), 18 cm solid limestone with Parag. patens, “G.costata (Figs. 5p–q, type level), Kaz. evoluta, Eoc. supradevonicus, Paralytoceras crispum (lower part of Parag. patens Zone, LD I-D), S. (S.) sandbergi, S. (S.) quadruplicata, S. (S.) belkai M1 (Figs. 2q-r), Ps. triangulus triangulus (Bed 2u), and Elictognathus bialatus (lower S. (S.) sandbergi Zone and Subzone).

Bed 3a, 10 cm nodular shale with abundant Pseud. westfalicus and Pseud. planissimus (top Pseud. westfalicus Zone, top LC I-C), S. (S.) sandbergi (record of Korn and Weyer 2003), S. (S.) cf. lobata (?= M2), and S. (S.) belkai M1 (basal S. (S.) sandbergi Zone and Subzone).

Bed 3b (Ziegler-Bed 13, Voges-Sample 8), 8–9 cm nodular limestone with G. crassa, Pseud. carinatus, Ac. (St.) depressum, “Mim.simile, N. acre (upper part of Pseud. westfalicus Zone, LC I-C), Ps. triangulus triangulus, S. (S.) cf. wilberti, and Pinacognathus profunda (top part of S. (S.) mehli Zone).

Beds 3c1-c2 (Ziegler-Beds 11–12, Voges-Sample 7), ca. 12 cm nodular limestone with Pseud. westfalicus, Pseud. subtilis, Eoc. brevis, Eoc. tener, Eoc. spiratissimus (Pseud. westfalicus Zone, LC I-C), S. (S.) belkai M1 (Fig. 2p), and S. (S.) lobata M2 (Fig. 2s) (S. (S.) mehli Zone).

Bed 3d (Ziegler-Bed-10, Voges-Sample 6), 9 cm limestone with Pap. raricostatus, H. gracilis (higher part of Parag. sphaeroides Subzone, LC I-B2), S. (S.) obsoleta, S. (S.) belkai M2, S. (S.) lobata M2, and S. (S.) cf. wilberti (higher part of S. (S.) mehli Zone).

Bed 3e (Ziegler-Bed 9), 4 cm limestone with Parag. sphaeroides (compare cf. specimen of Figs. 5n–o), Cost. ornatum, and Wey. molaris (Parag. sphaeroides Subzone, LC I-B2), not sampled for conodonts (possibly lower part of S. (S.) mehli Zone).

Beds 4a–b (Ziegler-Beds 7–8, Voges-Sample 5), 18 cm solid limestone with Pap. dorsoplanus, Gl. globiforme, H. multisulcata, “Mim.exile (Pap. dorsoplanus Zone/Subzone, LC I-B1), S. (S.) duplicata (Fig. 2m, Bed 4b, Fig. 2n, Bed 4a), S. (S.) lobata M2, Ps. marginata, Ps. triangulus inaequalis, protognathodids with atypical ornamentation (Fig. 2e–g) (S. (S.) duplicata Zone), and Liobolina nebulosa.

Bed 5b (Ziegler-Bed 5), 6 cm limestone with S. (Eo.) bransoni (Fig. 2l, S. (Eo.) bransoni Zone).

Bed 5c-d (Ziegler-Bed 4, Voges-Sample 3), 7 cm limestone with “Eoc.nodosus, V. peracutus, G. subinvoluta (Figs. 5l–m), G. involuta (= tenuis), “G.costata, “Wey.concava, “Mim.varicosum, “Mim.hoennense, Ac. (Str.) heterolobatum, N. trochiforme, and N. subacre (“Eoc.nodosus Subzone, LC I-A3).

Bed 6a (Kaiser 2005; Ziegler-Beds 2/3, Voges-Sample 2, Sacher-Beds 228b–230b, Luppold et al. 1994; Beds 6B–D), 20 cm solid limestone with G. subinvoluta, G. involuta (new record), Wey. reticula, H. sphaeroidalis, Ac. (Ac.) acutum, Ac. (St.) antecedens, Ac. (St.) undulatum, Ac. (St.) convexum (G. subinvoluta Zone/Subzone, LC I-A2), S. (Eo.) sulcata s.l., Pr. kockeli, “Po. spicatus”, Po. purus purus, Po. purus subplanus, Ps. primus. Ps. multistriatus (S. (Eo.) sulcata s.l./Pr. kuehni Zone); basal post-Crisis Interval.

Upper Stockum Limestone:

Bed 6b (Kaiser 2005; Sacher-Bed 227, Luppold et al. 1994, Bed 6A), ca. 5 cm nodular shale with carbonate sand clasts (Van Steenwinkel 1984) with S. (Eo.) sulcata s.l., Pr. kuehni, Pr.praedelicatus-cordiforme”, Pr. kockeli (partly transitional towards Pr. kuehni, Fig. 2h), Po. purus purus, Po. purus subplanus, reworked Pa. glabra pectinata and Bi. ultimus ultimus (Luppold et al. 1994), and other conodonts (basal S. (Eo.) sulcata s.l./Pr. kuehni Zone), Belgibole abruptirhachis, and Macrobole drewerensis Group; Upper Crisis Interval III.

- unconformity (basal VI Zone and Lower Stockum Limestone/kockeli Zone = Upper Crisis Interval I–II missing) -

Hangenberg Shale: Sacher-Beds 226a–b, ca. 6.5 m of greenish silty shale and thin siltstones with Postclymenia sp., Ac. (St.) cf. procedens, Ac. (St.) aff. antecedens, and Ac. (St.) cf. subbilobatum (auct.) (lower Ac. (St.) prorsum Zone, UD VI-F); Middle Crisis Interval I/II, LN Zone (Higgs in Becker et al. (1993).

Hangenberg Black Shale: Ca. 28 cm laminated shale with a sharp lower base, a main lower black shale (Sacher-Bed 225a, 8 cm), a middle dark-grey package (Sacher-Beds 225b–d, 17.5 cm), a thin upper black shale (Sacher-Bed 225e, 2 cm); with Post. cf. evoluta (Post. evoluta Zone, UD VI-E), basal LN Zone (Higgs and Streel 1994); transgressive Lower Crisis Interval.

Wocklum Limestone: Ca. 3.7 m, cyclic alternation of variably fossiliferous, nodular limestone, nodular and greenish-grey, calcareous shale. Bed numbers are those of Schindewolf (1937), with numbers in brackets from Sacher (2016). FODs and LODs of stratigraphically significant taxa are preferentially listed.

Bed 1 (220c–224b) with Epi. applanata, the last W. denckmanni (type level of the synonymous W. aperta Schindewolf, 1937, and W. plana Schindewolf, 1937; e.g. Beds 222b, 223b, 224b), P. paradoxa (e.g. Beds 220c, 220d), P. paprothae, F. wocklumensis (e.g. Bed 224b), Liss. wocklumeri, Cyrto. angustiseptata, Cyrto. plicata, “Cyrto.hexagona, N. Gen. “cf. stuckenbergi”, Sp. muensteri orbiculare, Ebbighausenites seidlitzi, May. nucleus, Ken. rostratum (= biforme), Balvia globularis, “Mim.liratum (e.g. Bed 223b), “Mim.lentum (e.g. Bed 220d) (Epi. applanata Subzone, UD VI-D2), the last Bi. costatus, Bi. ultimus ultimus, Bi. bispathodus, Bi. spinulicostatus, Br. suprema, Pa. gracilis gracilis, Pa. gracilis sigmoidalis, and Ps. marburgensis trigonicus (top S. (Eo.) praesulcata s.l. Zone), Po. obtectus, Elictognathus tylus, Dinodus cf. wilsoni, the last Rabienops granulatus, Rab. wedekindi wedekindi, Weyerites wocklumeriae, Dianops anophthalmus, Chaunoproetus (Ch.) palensis, Helioproetus subcariantiacus, and Semiproetus (Anglibole) anglicus.

Bed 2 (218b–220b) with W. denckmanni, P. paradoxa, P. paprothae, R. lineare (Bed 218b), and the LOD of Pa. gracilis gonioclymeniae (top former Middle costatus Zone).

Bed 3 (ca. 216b–217b) with W. denckmanni, P. paradoxa, F. wocklumensis, “C.barbarae, Postglatziella carinata, Discoclymenia cucullata, Ken. rostratum, and May. nucleus (UD VI-D1).

Bed 4 (ca. 215c–d) with W. denckmanni, P. paradoxa, P. paprothae, and F. wocklumensis (UD VI-D1).

Bed 5 (214b–215b) with Wocklumeria sp., P. paradoxa, P. paprothae, Postglatziella sp. juv., and Gen. nov. “cf. stuckenbergi” (a new cyrtoclymeniid genus with strongly flattened flanks and venter; base W. denckmanni Zone, UD VI-D1).

Bed 6 (ca. 213b–214a) with May. nucleus, Ken. rostratum, P. paradoxa, P. paprothae, and Gl. glaucopis (P. paradoxa to May. nucleus Subzones, UD VI-C2–3).

Bed 7 (ca. 212e–213a) with P. paprothae, P. distorta, P. patens, Kamp. trigona, Kamp. endogona, Tria. triangularis, and Gl. glaucopis (P. paprothae Subzone, UD VI-C1).

Bed 8 (ca. 212b–212d) with P. paprothae, P. distorta, P. patens, Kamp. trigona, Tria. triangularis, and Gl. glaucopis (P. paprothae Subzone, UD VI-C1).

Bed 9 (ca. 211a–212a) with P. paprothae, P. distorta, P. patens, Kamp. endogona, Kamp. trivaricata, Tria. triangularis, and M. falx (= Prionoceras nucleus n. mut. in Schindewolf 1937) (P. paprothae Subzone, UD VI-C1).

Bed 10 (ca. 208a–210b) with P. cf. paprothae, P. distorta, Tria. triangularis, Liss. wocklumeri, Gl. glaucopis, Gl. minervae, and the locally youngest Selwoodites n. sp. aff. cornwallensis (base P. paprothae Subzone, UD VI-C1).

Bed 11 (207a–b) with “Sph.brevispina, and Eff. lens (top UD VI-B).

Bed 12 (204b–206b) with “Sph.brevispina, Sph. aff. maxima, C. semistriata (e.g. Bed 204c), and Eff. lens (UD VI-B).

Bed 13 (202b–203b) with “Sph.brevispina, Sp. muensteri orbiculare, R. cf. quadripartitum, and Eff. lens (UD VI-B).

Bed 14 (202a), nodular shale with C. striata and questionable Effenbergia (UD VI-B).

Bed 15 (198b–201b) with Effenbergia lens (Prionoceras n. sp. IV in Schindewolf 1937, see comment by D. Weyer in Mottequin et al. 2019, p. 6), Glatziella, and K. pessoides (base Eff. lens Zone, UD VI-B).

Bed 16 (ca. 197a–198a) with K. cf. subarmata, “C.barbarae, Ebbighausenites seidlitzi, and rectimitoceratids (UD VI-A2).

Bed 17 (196a–196b) with K. cf. subarmata, “Sphenoclymenia” (UD VI-A1/2), and S. (Eo.) praesulcata (Kürschner et al. 1993, S. (Eo.) praesulcata s.l. Zone).

Bed 18 (ca. 194a–195b) with K. subarmata, Sp. muensteri orbiculare, and “Cyrto.tetragona (UD VI-A1/2).

Bed 19 (ca. 192a–193b) with K. uhligi and Ebbighausenites seidlitzi (UD VI-A1).

Bed 20 (ca. 188a–191b) with Discoclymenia cucullata, R. lineare, Bi. ultimus ultimus (Bed 191b, Sacher 2016), and Pr. meischneri (Kürschner et al. 1993).

Bed 22 (ca. 185a–187b) with “Sph.” cf. brevispina and the oldest Selwoodites n. sp. aff. cornwallensis, Pa. gracilis gonioclymeniae, and Br. suprema.

Bed 23 (ca. 181b–184b) with probable Linguaclymenia (recorded as Oxyclymenia bisulcata in Schindewolf 1937; perhaps base of L. similis Zone, UD VI-A1) and Ps. marburgensis trigonicus (Bed 181b, Sacher 2016; base Bi. ultimus ultimus Zone).

A corresponding, adjacent section that is now overgrown was exposed for a long time along the main road through the Hönne Valley (Luppold et al. 1994; Korn and Weyer 2003; both with section logs). The top Wocklum Limestone was very fossiliferous (with abundant W. denckmanni, F. wocklumensis, Cyrtoclymenia, Gl. glaucopis, and other ammonoids, RTB collection). Korn and Weyer (2003) mention an unpublished collection of ca. 3.000 ammonoid specimens from the Wocklum Limestone by a Tübingen Ph.D. student, and of further 500 specimens collected by D. Korn. This material includes probably further interesting records. Despite the only 200 m distance to the railway cut, the Hangenberg Shale is thicker and contains massive Hangenberg Sandstone beds. Two research boreholes, Oberrödinghausen 1 and 2, were drilled in 1979 and studied for conodonts (zonal identifications by W. Ziegler) and palynology (Higgs and Streel in Becker et al. 1993).

Discussion: The local DCB unconformity excludes the section from a re-consideration as a GSSP candidate, despite its enormous significance for ammonoid-conodont stratigraphy/correlation at levels below and above the Hangenberg Crisis Interval. This situation could have changed if the Hangenberg Extinction had been re-considered as the future DCB level, as proposed first by Paul (1937b, footnote on p. 748), and then by Walliser (1984). However, the majority of the DCB Task Group voted against this option in 2016.

The re-sampling of the basal Hangenberg Limestone by Sacher (2016: Bed 227) yielded an Upper Protognathodus Fauna with Pr. kockeli, Pr. kuehni, Po. purus purus, Po. purus subplanus, Neo. communis communis, Neo. communis namdipensis, Neo. talassicus, and other conodonts (several Bispathodus, including reworked Bi. costatus M2, and Mehlina) but not with a single siphonodellid. This fully supported the stratigraphic results of Kaiser (2005). It shows that there is a thin layer of Upper Stockum Limestone preserved and that the hiatus at the base of the limestone successions corresponds to the DCB regression known from Hasselbachtal. Luppold et al. (1994) reported a different fauna with Pr. kockeli, S. (Eo.) sulcata s.l. and different reworked Famennian conodonts from their corresponding Bed 6A. This faunal difference points to a complex mixture of reworking and condensation. It needs to be stressed that there is no record of any species of the Gattendorfia Fauna in Beds 6b = 6A = 227.

Hangenberg (Fig. 7)

Location: Trenches from 1973 at the Hangenberg near Deinstrop, northern Sauerland (Fig. 9), topographic sheet 4613 Balve, r 3 423 900/h 5 695 750.

Literature: Schmidt (1924a, b), Paeckelmann (1924), Paeckelmann and Kühne (1938), Stoppel 1977, Luppold et al. (1994).

Succession: Although this was the original type area for the Hangenberg Beds (now Hangenberg Formation) of Schmidt (1924a, b), there is hardly any outcrop. A trench dug in 1973 had to be filled quickly; it was measured by Leuteritz and Schäfer and described by Stoppel 1977. Luppold et al. (1994) provided details for natural outcrops in the vicinity. Both sources together give the following succession:

Kahlenberg Formation (Lower Alum Shale): Unfossili-ferous black shale, Lower Alum Shale Event Interval, middle Tournaisian.

Hangenberg Limestone:

1.3 m grey limestone, compact in the lower part, more nodular in the upper part, rich in conodonts in the first thick bed (Samples III–X) but still without zonation for the main and upper parts; with protognathodids (Fig. 2a–d).

A few cm of solid limestone (Sample II) with S. (Eo.) sulcata s.l. (S. (Eo.) sulcata s.l./Pr. kuehni Zone), probably basal post-Crisis Interval.

Lower Stockum Limestone: Thin, silty limestone layer at the base of the Hangenberg Limestone (Sample I) with Pr. kockeli, Protognathodus sp. 1 and sp. 2 (unusually ornamented morphs), Po. purus subplanus, Ps. vogesi, and probably reworked Bi. ultimus ultimus (recorded as Bi. ziegleri ziegleri) and Pa. gracilis gracilis (Pr. kockeli Zone), Upper Crisis Interval II.

Hangenberg Sandstone: Ca. 22 m alternating olive-grey or dark-grey shales, silty shales, siltstones, and micaceous, calcareous sandstones, Middle Crisis Interval II.

Hangenberg Shale:

Bed of bluish-grey, argillaceous limestone without any fauna; local Middle Crisis Interval Ib.

Ca. 6.5 m platy, olive-grey to dark-grey shale, local Middle Crisis Interval Ia.

Bed of reddish, strongly micaceous sandstone (Stoppel 1977), base ckI.

- unconformity (no Hangenberg Black Shale; eroded?) –

Wocklum Limestone:

Fossiliferous bluish-grey limestone with Wocklumeria (W. denckmanni Zone, UD VI-D), Bi. costatus, Bi. ultimus ultimus (recorded as Bi. ziegleri ziegleri), B. muessenbergensis, Pa. gracilis ssp. (three subspecies), Br. suprema, and Ps. marburgensis trigonicus (top S. (Eo.) praesulcata s.l. Zone) at the top (Bed 1, Crisis Prelude).

Discussion: The presence of a limestone unit at the boundary between Hangenberg Shale and Hangenberg Sandstone in the section of Leuteritz and Schäfer was regionally unique. Unfortunately, it was unfossiliferous.

Dasberg (Fig. 7)

Location: Although the Dasberg ca. 1 km WNW of Hövel (northern Sauerland, Fig. 9, sheet 4613 Balve, ca. r 3 424 100, h 5 693 400) provided the name for the Dasberg Formation and Dasberg-Stufe (Dasbergian), there are only very small natural outcrops. The knowledge of precise conodont and ammonoid stratigraphy, therefore, is based on temporary trenches (e.g. Schindewolf 1937; Schäfer 1976). Only the trenches of D. Korn dug in the late eighties made the uppermost Famennian available (Clausen and Korn 2008).

Literature: Denckmann and Lotz (1900), Denckmann (1902), Wedekind (1914: type locality of Costaclymenia kiliani), Schmidt (1924a, b: type locality of Oxyclymenia undulata var. coronata, C. striata var. serpentina, and Sellaclymenia spinosa), Paeckelmann (1924), Richter and Richter (1926), Lange (1929: type locality of Oxy. bisulcata var. colubrina), Paeckelmann and Kühne (1938), Paul (1939b), Schäfer (1976), Korn (1981a, 2017), Korn and Luppold (1987), Korn and Price (1987), Price and Korn (1989: type locality of Sph. erinacea), Clausen and Korn (2008), Korn et al. (2018), Korn and Price (2018, 2019: type locality of Finiclymenia langei).

Summary of succession: The following account of the Wocklum Limestone, with a focus on levels with FODs, is based on Clausen and Korn (2008).

Bed A, 11 cm, three layers of nodular limestone with Kamp. endogona, Kamp. trigona, P. distorta, Mim. fuerstenbergi, and Liss. wocklumeri.

Bed B, 21 cm, three layers of partly solid nodular limestone and overlying shale with P. paprothae, P. patens, Eff. falx, and Ken. rostratum (base P. paprothae Subzone, UD VI-C1).

Bed D, 13 cm, three layers of nodular limestone with Kos. schindewolfi, Eff. minutula, Soliclymenia solarioides, M. ademmeri, and Gl. glaucopis (top of Eff. lens Zone, top UD VI-B).

Bed E, 19 cm, three layers of nodular limestone and intervening shale with Mim. trizonatum.

Bed F, 22 cm, seven layers of nodular limestone with Eff. lens (base Eff. lens Zone, UD VI-B).

Bed I, 22 cm, six levels of limestone nodules and nodular limestone with M. bisulcata and M. parundulata (base M. bisulcata Zone, UD VI-A2).

Bed K, 21 cm, five levels of limestone nodules, nodular limestone and intervening shale with M. galeata, Kos. undulata, and “Mim.geminum (upper part of L. similis Zone, upper UD I-A1).

Bed L, 24 cm, four levels of nodular limestone followed by shale with L. similis, M. sublaevis, Kalloclymenia sp., Cyrto. angustiseptata, Sph. erinacea (type level, formerly Bed 0), and Mim. alternum (lower L. similis Zone, lower UD VI-A1).

Discussion: The rich ammonoid fauna of Korn’s trenches is very important since it considerably supplements the Oberrödinghausen, Müssenberg, Hasselbachtal, and Effenberg records, proving several range additions.

Effenberg (Fig. 7)

Location: Active quarry E of the road from Enkhausen to Herdringen, northern Sauerland (Fig. 9), topographic sheet 4613 Balve, r 2 527 700/h 5 695 950.

Literature: Paeckelmann (1924), Schmidt (1924a, b: type locality of Chaenocardiola elongata), Richter and Richter (1926), Paeckelmann and Kühne (1938), Paul (1939b), Korn (1981a, 1992a, 2004, 2017: type locality of Gonioclymenia wunderlichi), Paproth et al. (1986b), Korn and Luppold (1987), Korn and Price (1987: type localities of K. (K.) undulata effenbergensis from UD V-C and K. (M.) parundulata from UD VI-B), Price and Korn (1989), Korn in Becker et al. (1993), Luppold et al. (1994), Greifelt (2008), Hartenfels and Becker (2009), Hartenfels (2011), and Hartenfels and Becker (2016).

Summary of succession: The section in the NW corner of the quarry, where mining activities near the property margin stopped many years ago, exposes the top Hemberg Formation and Dasberg Formation, including the Wocklum Limestone, which are partly very fossiliferous and marked by the global Annulata Events and the Dasberg Crisis (e.g. Korn and Luppold 1987; Hartenfels and Becker 2009; Hartenfels 2011). A new bed-by-bed survey of the Dasbergian/Wocklumian transition and Wocklum Limestone started in autumn 2017 but there are still only preliminary ammonoid data; a first set of conodont samples has been processed but not yet been analysed. The DCB succession is currently exposed between several tracks within the SE part of the quarry but this outcrop has not yet been investigated in detail; probably, it will not persist in the future. DCB knowledge summarised here is based on data and bed numbers in Korn and Luppold (1987) and Luppold et al. (1994).

Kahlenberg Formation (Lower Alum Shale): 2 m bleached black shale, Lower Alum Shale Event Interval, middle Tournaisian.

- ?unconformity (no upper part of Hangenberg Limestone) -

Hangenberg Limestone:

Beds 18 m–o, condensed nodular limestone with “S. duplicata” (S. (S.) bransoni to S. (S.) duplicata Zones).

Bed 18f–l, condensed nodular limestone with Pr. kuehni and S. (Eo.) sulcata s.l. (lower S. (Eo.) sulcata s.l./Pr. kuehni-Zone), post-Crisis Interval, lower Tournaisian.

Stockum Limestone:

Beds 18c–e, condensed nodular limestone with acutimitoceratids, transitional forms between Pr. kockeli and Pr. kuehni (top Pr. kockeli to Pr. kuehni Zones) and Po. purus subplanus, Lower/Upper Stockum Limestone, Upper Crisis Interval II/III.

Beds 18a–b, condensed nodular limestone with acutimitoceratids, Pr. kockeli (Pr. kockeli Zone), Lower Stockum Limestone, Upper Crisis Interval II,

Ca. 3 cm shale.

Ca. 3 cm calcareous shale with Guerichia mass occurrence, Pr. collinsoni and Pr. kockeli (Pr. kockeli Zone), Upper Crisis Interval II.

Hangenberg Sandstone: Ca. 20 cm siltstone.

Hangenberg Shale: 6 cm shale, slightly darker than the succession above.

- minor unconformity (no Hangenberg Black Shale) -

Wocklum Limestone: The lower part has the richest ammonoid faunas of the outcrop, partly forming kosmoclymeniid coquinas (Hartenfels et al. 2016, fig. 13). This level also yielded C. semistriata (Figs. 5i–j), abundant “Mimimitoceras”, K. subarmata, and giant-sized members of the “K.pachydisca Group (Hartenfels et al. 2016, fig. 12).

Top ca. 10 cm with Ps. marburgensis trigonicus, Bi. muessenbergensis, Bi. ultimus ultimus (reported as Bi. ziegleri ziegleri), Br. suprema, and three subspecies of Pa. gracilis (top S. (S.) praesulcata s.l. Zone), pre-Crisis Interval/Crisis Prelude.

Cliff of solid nodular limestone above Bed 29 with P. paradoxa (P. paradoxa Subzone, UD VI-C2).

Bed 23a, level of thick nodules with K. subarmata (?upper part of L. similis Zone, UD VI-A) and only long-ranging conodonts. The relationships with “Bed 93d”, the type level of M. parundulata Korn and Price, 1987, an alternative index species for the M. bisulcata Zone (UD VI-A2), have not been published.

Bed 19, nodule level with “Sph.brevispina (L. similis Zone, UD VI-A1) and Pa. gracilis gonioclymeniae (Bi. ultimus ultimus Zone).

Bed 17a, nodule level with “Sph.brevispina (L. similis Zone, UD VI-A1), basal uppermost Famennian.

Discussion: The strong condensation of DCB beds and the ongoing quarrying disqualify the section for the GSSP search.

Müssenberg (Fig. 7)

Location: Trenches of D. Korn at the Müssenberg N of Hachen and S of Neheim-Hüsten, northern Sauerland (Fig. 9), topographic sheet 4613 Balve, r 3 429 280, h 5 695 320.

Literature: Denckmann and Lotz (1900), Richter and Richter (1926: record of Phacops granulatus), Korn (1981a, 1981b, 1989, 1992a, 1993), Paproth and Streel (1982), Luppold et al. (1984, 1994), Brauckmann and Hahn (1984), Korn and Price (1987), Korn and Luppold (1987), Clausen et al. (1989b), Hahn et al. (1990: type locality of Belgibole abruptirhachis korni), Becker and Weyer (2004), Clausen and Korn (2008), Klein and Korn (2016), Korn (2017: type loca-lity of Gonioclymenia pricei from UD V-C), Korn et al. (2016), Korn and Price (2018, 2019: type locality of F. czarnockii), Feist and Weyer (2018).

Summary of succession: Müssenberg-1 section.

Hangenberg Limestone: Condensed, partly crinoidal cephalopod limestone.

Bed 0 with S. (S.) carinthiaca, “S. duplicata” s.l., and Ps. triangulus triangulus (S. (S.) mehli Zone).

Bed 1 with “S. duplicata” s.l., Ps. triangulus triangulus (?basal S. (S.) mehli Zone), “V. peracutus” (re-identified as an early karagandoceratid by Korn and Weyer 2003 and Becker and Weyer 2004), G. cf. involuta (= cf. tenuis) ("Eoc". nodosus Subzone, LC I-A3), and Diacoryphe strenuispina.

Bed 2 with Ps. triangulus inaequalis (S. (S.) duplicata Zone) and Cyrtoproetus cf. blax.

Bed 3C with S. (Eo.) sulcata s.l., “S. duplicata” s.l. (probably S. (Eo.) bransoni Zone), reworked Pa. gracilis gracilis and Bi. costatus, and G. subinvoluta (G. subinvoluta Subzone, LC I-A2).

Upper Stockum Limestone: Grey cephalopod limestone.

Bed 3B with Ac. (St.) intermedium (auct.) and C. striata, the youngest known clymeniid (top LC I-A1).

Bed 3A with Ac. (St.) stockumense, Ac. (St.) procedens, and other acutimitoceratids (middle LC I-A1).

Bed 3a with Pr. kuehni, Pr. kockeli, S. (Eo.) sulcata s.l. (section Müssenberg-4), Po. purus purus (basal S. (Eo.) sulcata s.l./Pr. kuehni Zone), Ac. (St.) intermedium, (auct.) Ac. (St.) kleinerae, Ac. (Str.) carinatum (upper Ac. (St.) prorsum Zone, lower LC I-A1), Macrobole cf. funirepa (also reported as Phillibole drewerensis), Waribole superna, and Belgibole abruptirhachis korni (type level); transgressive Upper Crisis Interval III.

- minor unconformity (no Hangenberg Sandstone and Lower Stockum Limestone) -

Hangenberg Shale: 1 cm greenish, silty shale with weathered pyrite, Middle Crisis Interval.

Base Bed 3: Main Hangenberg Extinction, base ckI.

- minor unconformity (no Hangenberg Black Shale) –

Wocklum Limestone: Cyclic alternation of bioturbated, micritic cephalopod limestones, partly with Stromatactis structures, nodular shales and calcareous shales. Ammonoid ranges mostly from Korn (1993) and Klein and Korn (2016).

Bed 4 with the last P. paradoxa (top W. denckmanni Zone, UD VI-D), Bi. costatus, Bi. ultimus ultimus, Br. suprema, Pa. gracilis ssp. (three subspecies), Ps. marburgensis trigonicus (top S. (Eo.) praesulcata Zone), Haasia antedistans, and Silesiops cf. schindewolfi; Crisis Prelude.

Bed 5 with mass occurrences of Wocklumeria and Lissoclymenia as indicator of increased condensation, with Waribole warsteinensis and Chaunoproetus; basal Crisis Prelude.

Bed 13 with W. denckmanni and C. involvens (base W. denckmanni Zone, UD VI-D) and trilobites.

Bed 14 with a rich trilobite fauna (Rabienops wedekindi, Weyerites cf. wocklumeriae, Chaunoproetus, Skemmatopyge, Haasia, Typhloproetus, Silesiops, Waribole: nine species in total).

Beds 19–17 with May. nucleus, Ken. rostratum (= biforme), F. wocklumensis, and Postglatziella carinata (base May. nucleus Subzone, UD VI-C3).

Bed 25 with P. paradoxa, Mim. trizonatum, “Mim.lentum, and B. globularis (base P. paradoxa Subzone, UD VI-C2).

Bed 29 with Liss. wocklumeri and Mim. fuerstenbergi (higher P. paprothae Subzone, upper UD VI-C1).

Bed 34 with P. paprothae, Kamp. endogona, Kamp. endogona, Gl. glaucopis, K. schindewolfi, L. clauseni, Mim. trizonatum, Eff. falx, and B. globularis (base P. paprothae Subzone, UD VI-C1).

Bed 38 with Eff. lens (base Eff. lens Zone, UD VI-B).

Bed 54 with “Mim.geminum (higher M. bisulcata Zone, UD VI-A2).

Bed 55 with S. (Eo.) praesulcata s.l. (base S. (Eo.) praesulcata Zone).

Bed 67 with M. bisulcata and M. parundulata (base M. bisulcata Zone, UD VI-A2).

Bed 78 with K. subarmata (higher L. similis Zone, UD VI-A1).

Bed 80 with Bi. ultimus ultimus (recorded in Luppold et al. 1994 as Bi. ziegleri ziegleri) and Pa. gracilis gonioclymeniae.

Bed 83 with Br. suprema and Kos. undulata (L. similis Zone, UD VI-A1).

Bed 85 with Ps. marburgensis trigonicus (base Bi. ultimus ultimus Zone) and “Sph.brevispina (ca. base of former “Sph.” brevispina Zone).

Bed 90 with L. similis, M. sublaevis, K. undulata, Post. warsteinensis, Cyrto. plicata, Rodachia dorsocostata, and “Mim.liratum (base L. similis Zone, UD VI-A1).

Discussion: The Müssenberg trenches provided the best current record for the definition of the Rhenish Wocklum-Stufe (Wocklumian) and for its ammonoid zonation, especially in its lower part (interval of the former K. subarmata Zone sensu Schindewolf 1937). The DCB unconformities exclude it from any GSSP discussions.

Reigern Quarry, Hachen

Location: Mostly filled and overgrown old quarry in the forest ca. 500 m N of Hachen, northern Sauerland (Fig. 9), topographic sheet 4613 Balve, r 3 429 770/h 5 695 230 (GPS 51° 23′ 15.77″, N 7° 59′ 25.20″).

Literature: See compilation in the recent review by Söte et al. (2017). Subsequently, a Sphenoclymenia brevispina from Reigern was figured by Korn and Price (2019).

Succession: The Reigern Quarry is a very important locality for ammonoids from the lower part of the Wocklum Limestone (Korn 1981a, 1988b; Price 1982; Korn and Price 1987; Price and Korn 1989). The recent conodont study by Söte et al. (2017) proved the presence of the Bi. ultimus ultimus (Beds 1–23) and S. (Eo.) praesulcata s.l. Zones (Beds 24–39). The DCB is marked by a long-lasting major unconformity, with non-deposition starting before the base of the P. paprothae Subzone (UD VI-C1) and lasting until the Viséan.

Burgberg near Wocklum (“Borkewehr”)

Location: Forest track and old quarry at the SW slope of the Burgberg near Wocklum-Mellen, northern Sauerland (Fig. 9), topographic sheet 4613 Balve, r 3 422 050, h 5 688 650 (see quarry sketch in Schmidt and Pleßmann 1961, fig. 4).

Literature: Denckmann (1901), Wedekind (1918: type locality of Epi. applanata and W. denckmanni), Paeckelmann (1924), Schmidt (1924a, 1924b: first section measurements), Richter and Richter (1926), Schindewolf (1926), Lange (1929: type locality of C. involvens and F. wocklumensis), Matern (1929), Rabien (1954), Bischoff (1957: type locality of Bi. ultimus ultimus, Pr. kockeli, and Tripodellus robustus), Voges (1959, 1960), Schmidt and Pleßmann (1961), Streel (1969: failed attempt to find DCB spores), Eickhoff (1970; type locality of Hyperammina aperta and ?Moravammina constricta), Ziegler (1971), Price and Korn (1989), Luppold et al. (1994), Becker (1996, 2000), Becker et al. (2016a), Becker and Hartenfels (2017), Hartenfels et al. (2017a, b), Hartenfels and Becker (2018, 2019), Korn and Price (2019: revision of F. wocklumensis), Herbig et al. (2019).

Discussion: The Burgberg or Borkewehr section is an important DCB GSSP candidate since it records the sharp Hangenberg Extinction of ammonoids and conodonts, the subsequent Hangenberg Black Shale, equivalents of the Hangenberg Shale and Sandstone, and, notably, the early protognathid evolution after the Hangenberg Regression. For a refined section log see Becker et al. (2016a). A new bed-by-bed study of ammonoids, conodonts, corals, microfacies, and geochemistry has been completed and will be presented in 2021 in a separate contribution to this journal.

Stockum Trenches (Figs. 7, 13)

Location: Forest track slope and various adjacent trenches on the southern slope of the Spitze Kahlenberg, 900 m ESE of Stockum, sheet 4713 Plettenberg, ca. r 3 430 190, h 5 684 600 (Fig. 9).

Fig. 13
figure13

Summary section log for the DCB transition at Stockum (re-drawn from the section log of Clausen et al. 1994, fig. 6) showing the occurrences of marker conodonts, ammonoids, and miospore zones. For abbreviated zones and lithological units see Fig. 1; for references to the numerous records see text; for lithology types see legends of Figs. 6, 7

Literature: Henke (1924), Schmidt (1924a), Schmidt (1924b: type locality of Aganides carinatus, Pleurotomaria (Mourlonia) Henkei, and Spiriferina tarpata; 1925: type locality of Aganides prorsus), Gallwitz (1928), Richter and Richter (1951), Weyer (1965a, 1977), Ziegler (1969: type locality of Pr. meischneri and Pr. collinsoni, 1970), Alberti et al. (1974), Paproth and Streel (1982), Brauckmann and Hahn (1984), Keupp and Kompa (1984), Kasig et al. (1984), Bless and Groos-Uffenorde (1984), Korn (1984, 1994), Hahn et al. (1990), Higgs et al. (1993), House (1993), Clausen et al. (1989b, 1994: detailed locality maps and revision), Higgs and Streel (1994), Streel and Korn et al. (2016), Mottequin et al. (2019).

Summary of succession: Results from the different trenches can be combined to a synthetic DCB section, giving both the units of Alberti et al. (1974: Alb-letters) and the more detailed bed numbering of Clausen et al. (1994):

Kahlenberg Formation (Lower Alum Shale):

Unit Alb-E, 5 m black shale, in the upper part with cherts, with S. (S.) crenulata, S. (S.) quadruplicata, and Ps. pinnatus (Samples 351–350, Trench III; S. (S.) crenulata Zone), Lower Alum Shale Event Interval, middle Tournaisian.

Basinal Shale equivalents of Hangenberg Limestone (no valid member name, included as an upwards extension in the “Hangenberg Shale” in Korn 2010, or included in undivided “Hangenberg Schichten” in Herbig et al. 2018):

Unit Alb-D, 36 m greenish-grey, silty shales with some micaceous and calcareous silt and sandstones and limestone concretions, among ostracods first with Richterina (R.) latior (Sample 891), higher with abundant Maternella cf. arcuata and M. schindewolfi; type level of Ungerella postmulticostata and U. stockumensis. Conodont succession of Groos-Uffenorde and Uffenorde (1974):

Sample 353 (Trench III): first S. (S.) lobata (S. (S.) lobata M1 Subzone).

Sample 919 (Trench III): local first S. (S.) obsoleta.

Sample 921 (Trench III): first S. (S.) sandbergi and Ps. triangulus triangulus (S. (S.) sandbergi Zone and Subzone).

Samples 321–322 (Trench I) and Sample 325 (Trench III): S. (S.)?quadruplicata (S. (S.) mehli Zone).

Sample 918 (Trench III): first S. (S.) cooperi (S. (S.) mehli Zone).

Sample 316 (Trench I): first S. (S.) “duplicata s.str.” (S. (S.) duplicata Zone.

Sample 315 (Trench I, ca. 5.2 m above Stockum Limestone s.str.): first Ps. triangulus inaequalis (S. (S.) bransoni to S. (S.) duplicata Zone).

Bed 95 (upper part of Unit Alb-C-e), 15–25 cm calcareous sandstone with S. (S.) aff. duplicata (S. (S.) bransoni to S. (S.) duplicata Zones), post-Crisis Interval.

Bed 97 (lower part of Unit Alb-C-e), 15–25 cm pyritic, calcareous sandstone with Pr. kuehni, Bi. spinulicostatus, Po. purus subplanus (Samples 331, 305), and others (S. (Eo.) sulcata s.l./Pr. kuehni Zone), miospores of the VI Zone, probably basal post-Crisis Interval.

Stockum Limestone:

Beds 98–99 (Unit Alb-C-d), 20–30 cm silty and micaceous shale with miospores of the VI Zone, ca. top Crisis Interval.

Bed 100 (Unit Alb-C-c), up to 8 cm-thick, dark-grey, sandy limestone (lower micrite cut off by a higher tempestite layer), rich in juvenile goniatites (acutimitoceratids) and conodonts, with Pr. kuehni (Sample 330 of Alberti et al. 1974), Pr. kockeli, Ps. fusiformis, and other conodonts (basal S. (Eo.) sulcata s.l./Pr. kuehni Zone), and trilobites (Belgibole abruptirhachis abruptirhachis, Macrobole funirepa; Sample 200), Upper Stockum Limestone, Upper Crisis Interval III.

Beds 101–102 (upper Unit Alb-C-b), ca. 35 cm silty shales with Belgibole abruptirhachis abruptirhachis, Macrobole funirepa (Sample 923), and miospores of the basal VI Zone, basal Upper Crisis Interval III.

Bed 103 (middle Unit Alb-C-b), Stockum Limestone lenses s.str., very fossiliferous, dark-grey limestone lenses (biopelmicrite to cephalopod rudstone with recognisable sublayers), up to 8 cm thick, with abundant goniatites (type level of Ac. (St.) prorsum, Ac. (St.) stockumense, Ac. (Str.) carinatum, and Ac. (Str.) caesari; upper part of Ac. (St.) prorsum Zone, LC I-A1), Pr. kockeli, Pr. collinsoni, Ps. nodomarginatus, and other conodonts (upper Pr. kockeli Zone), ?Texathyris tarpata (type level), Belgibole abruptirhachis abruptirhachis, top Lower Stockum Limestone, top Upper Crisis Interval II.

Beds 104–106 (lower Unit Alb-C-b), 40 cm silty shale to micaceous siltstone, including a level of very solid, dark-grey, laminated, pyritic limestone concretions (Bed 105) up to 30 cm in diameter, with Pr. kockeli, Pr. meischneri, Pr. collinsoni, Neo. communis dentatus, and other conodonts (Pr. kockeli Zone), and with Belgibole abruptirhachis abruptirhachis, Macrobole ogivalis, Macrobole duodecimae, and other trilobites (Samples 102, 923), ostracods (Maternella species), Guerichia, and miospores of the upper, atypical LN Zone, middle Lower Stockum Limestone, middle Upper Crisis Interval II.

Beds 107–108 (top Unit Alb-C-a), two thin limestone beds with Pr. kockeli, Pr. meischneri, Neo. communis communis, and S. (Eo.) praesulcata.l. (Sample 303, basal Pr. kockeli Zone), basal Lower Stockum Limestone, basal Upper Crisis Interval II.

Hangenberg Shale/Sandstone:

Bed 109 (Unit Alb-C-a), 50 cm calcareous and micaceous sandstone, Middle Crisis Interval.

Beds 110–119 (upper Unit Alb-C), ca. 3.3 m alternating greenish-grey, silty, micaceous shales, upwards increasingly with sandstones, with miospores of the upper, atypical LN Zone, Middle Crisis Interval II.

Beds 120–157 (lower/middle part of Unit Alb-C), ca. 9.5 m greenish-grey, silty, micaceous shale alternating with thin, partly laminated or calcareous, micaceous silt and sandstones, with a solid sideritic level (Bed 153) and a weathered, dark-grey, argillaceous, unfossiliferous limestone (Bed 152) in the lower part, and with miospores of the LN Zone, Middle Crisis Interval I; Sample 886 from the ca. lower meter with Richterina (Richt.) costata and Richt. (Richt.) striatula (hemisphaerica-latior Interregnum).

Beds 158–161 (ca. top Unit Alb-B), ca. 50 cm greenish-grey silty shale, Middle Crisis Interval I.

Hangenberg Black Shale:

Bed 162 (within higher Unit Alb-B), ca. 35 cm black shale, base of LN zone (Higgs and Streel 1994), Lower Crisis Interval.

Basinal Shale equivalents of Wocklum Limestone (no modern formation name):

Beds 163–187 (lower/middle Unit Alb-B), 7.2 m greenish-grey to brownish, silty shales with thin, dark-grey limestones in the middle (Bed 172) and upper parts (Beds 163–165), with Bi. ultimus ultimus (including Bi. ziegleri, Bed 187 and Sample 933, ca. 8 m below), Bi. costatus (Bed 187), Bi. muessenbergensis (Bed 172), Br. suprema (Bed 172), Ps. marburgensis trigonicus (Bed 187), Pa. gracilis gonioclymeniae (Bed 187 and Sample 933, see Groos-Uffenorde and Uffenorde 1974), Pa. gracilis gracilis, and Pa. gracilis sigmoidalis (Bi. ultimus ultimus to S. (Eo.) praesulcata s.l. Zones); ostracods of the Maternella (Mat.) hemisphaeria-Mat. (Mat.) dichotoma Zones (Samples 889 and 890, 15–17.5 m below the Stockum Limestone s.str.) and trilobites (Dianops, Weyerites, Typhloproetus, Chaunoproetus, Drevermannia; Samples 202, 203); uppermost Famennian, pre-Crisis Interval to Crisis Prelude.

Discussion: The initial major significance of the Stockum Limestone lenses was the discovery of a distinctive conodont and ammonoid fauna that differs strictly from the pre-Crisis (typical topmost Devonian) Wocklumeria and post-Crisis (typical basal Carboniferous) Gattendorfia faunas. Since a similar fauna was lacking at Oberrödinghausen, it became clear that the stratotype includes a significant gap right at the boundary, which disqualified it and led to the search for a new DCB GSSP. Subsequently, a succession of Protognathodus faunas (meischneri/collinsoni–kockeli–kuehni) was established, which shows that the larger Stockum Limestone interval comprises in various localities up to three different levels (here: Upper Crisis Interval I–III). At Stockum, “older” (without Pr. kuehni) and “younger” (with Pr. kuehni) Protognathodus faunas were distinguished since Alberti et al. (1974); they characterise the Lower and Upper Stockum Limestone sensu Becker et al. (2016a). The re-sampling by Clausen et al. (1994) of the main goniatite limestone of Schmidt (1924a, b), Bed 103, did not reproduce the Alberti et al. (1974) and Groos-Uffenorde and Uffenorde (1974) records of Pr. kuehni. This led to the assumption that the kuehni level was the slightly younger, thin Bed 100 of Clausen et al. (1994), which is also rich in goniatites, but mostly only in juveniles. The presence of Po. marginvolutus and of pseudopolygnathids in Bed 103 (Luppold and Stoppel in Clausen et al. 1994, Streel and Korn 2016) is not typical for conodont faunas of the kockeli Zone of other Rhenish localities.

E of Weninghausen (Fig. 7)

Location: Former slopes along a track branching off to the N from the road from Linnepe to Wenighausen, sheet 4614 Arnsberg, ca. r 3 435 120 /h5 687 125 (Fig. 9).

Literature: Gallwitz (1928), Kühne (1938).

Succession: The shelf basin facies between the Stockum area and the seamount settings of the drowned Warstein, Belecke, and Brilon reefs towards the E/NE is mostly poor in macrofauna. The recognition of the Crisis Interval in the undivided, more monotous, shaly Hangenberg Formation is difficult and hampered by the lack of outcrops. As an exception, Gallwitz (1928) described a succession from the E of Weninghausen:

Kahleberg Formation: 20 m Lower Alum Shale with a sharp base, Lower Alum Shale Event Interval, middle Tournaisian.

Hangenberg Limestone equivalents: 34 m solid, dark-greenish to bluish-grey shales with large, bluish, quartzitic concretions and intercalated, up to 40 cm thick beds of sandy, very hard, reddish to violet limestone, post-Crisis Interval.

Stockum Limestone equivalent: 1.2 m dark marls and greenish, partly micaceous shale with Ac. (St.) prorsum (re-assigned to Ac. (St.) substriatum in Kühne 1938), Ac. (St.) infracarbonicum, ?Texathyris tarpata, and bivalves, Upper Crisis Interval.

Hangenberg Shale/Sandstone: Ca. 6 m greenish-grey shales with thin-bedded, calcareous, and micaceous sandstones, Middle Crisis Interval.

Wocklum Limestone equivalents:

Dark, calcareous shales with Semiproetus (Anglibole) cf. anglica, Drevermannia schmidti, Weyerites, and Dianops, ?Crisis Prelude.

15 cm argillaceous, brownish weathering limestone, ?regressive Crisis Prelude.

Ca. 8 m greenish-grey, calcareous shales with some argillaceous, reddish-grey limestone beds with Dianops anophthalmus, pre-Crisis Interval.

Eastern Sauerland (Belecke to Brilon regions)

Drewer (Figs. 7, 14)

Location: Abandoned and partly filled quarry (“Provinzialsteinbruch“) 1 km SW of Drewer and 2 km N of Belecke, NE Sauerland (Fig. 9), topographic sheet 4526 Belecke, at r 5 555 000, h 6 710 000. The section is situated in the core of the 2nd order Belecke Anticline.

Fig. 14
figure14

Synthetic DCB succession of the Provincial Quarry Drewer near Belecke, showing occurrences of index ammonoids and conodonts, originally re-drawn from Clausen and Korn (2008), here updated from Becker et al. (2016b). For abbreviated zones and lithological units see Fig. 1; for references to the numerous records see text, * = reworked; for lithology legend see Fig. 13

Literature: A complete compilation was given by Becker et al. (2016b). Especially important are the papers by Schmidt (1922, 1924a, b), Schindewolf (1923b, 1926), Clausen and Leuteritz (1979b), Clausen et al. (1987, 1989a), Hahn et al. (1990), Korn (1991), Becker (1993, 1999), Korn et al. (1994b), Leuschner (1994), Clausen and Korn (2008), and Kumpan et al. (2015). New Drewer ammonoid specimens were included in Korn et al. (2016), Herbig (2016), Korn (2017), Korn and Price (2019), and Herbig et al. (2019).

Summary of succession: Sixteen lateral sections have been measured and sampled along the western and northern quarry walls (Korn 1991). Their correlation led to a synthetic succession with conodont and ammonoid ranges (Korn 2002; Clausen and Korn 2008; Becker et al. 2016b). It is not possible to plot unequivocally the samples and conodont faunas of the strongly condensed sections at the NE Wall of Clausen et al. (1987, 1989a). The updated synthetic succession is as follows:

Belecke Member of Eichenberg Formation (Lower Alum Shale):

Ca. 1 m of black, pyritic and anoxic/euxinic (high U/Th ratios), unfossiliferous, laminated alum shales (middle Tournaisian).

Transgressive and anoxic/euxinic Lower Alum Shale Event at the sharp base.

Hangenberg Limestone: Strongly cyclic alternation of light- to middle-grey nodular limestone and calcareous shale, poor in macrofauna.

Bed 13 (= 9a) with S. (Eo.) isosticha and S. (S.) quadruplicata (top S. (S.) lobata M1 Subzone).

Bed 12 (= 9b) with S. (S.) lobata and S. (S.) quadruplicata (S. (S.) lobata M1 Subzone).

Bed 10 (= ca. 10a) with Pseudarietites sp. (Pseud. westfalicus Zone, LC I-C).

Bed 9a (= 10d) with S. (S.) obsoleta and Ps. triangulus inaequalis (top S. (S.) mehli Zone to basal S. (S.) sandbergi Zone).

Beds 8/9 (= 11a) with S. (S.) mehli, S. (S.) quadruplicata (morphotype unknown), and S. (S.) cf. wilberti (upper part of S. (S.) mehli Zone).

Beds 6/7 (= 11b/c) with S. (S.) cooperi M2, S. (S.) carinthiaca, S. (S.) duplicata (M2), and Ps. triangulus triangulus (lower part of S. (S.) mehli Zone).

Bed 5 (= 11d) with S. (Eo.) bransoni (S. (Eo.) bransoni Zone).

Bed 4 (= 12) with S. (Eo.) sulcata s.l. (Fig. 2j, k) (S. (Eo.) sulcata s.l./Pr. kuehni Zone).

Bed 3a (= 13a) with “Eocanites” sp. (“Eoc.” nodosus Subzone, LC I-A3) and S. (Eo.) sulcata s.l. (S. (Eo.) sulcata s.l./Pr. kuehni Zone); a local new record of Ac. (Str.) heterolobatum (Figs. 5r–q) comes from a loose block with Po. purus purus, Neopolygnathus, and siphonodelloids.

Bed 3 (= 13b) with Gattendorfia sp. and Ac. (St.) kleinerae (G. subinvoluta Subzone, LC I-A2), Pr. kuehni (Bed 13b, Clausen et al. 1989a), S. (Eo.) sulcata s.l. (section NF), Ps. primus primus (= dentilineatus), Po. purus purus (basal S. (Eo.) sulcata s.l./Pr. kuehni Zone), and Liobolina submonstrans; basal Post-Crisis Interval.

Stockum Limestone: Middle- to dark-grey nodular limestones and marls with conodonts of the Protognathodus Biofacies.

?Upper Stockum Limestone, Bed 2 (= 13c) with Ac. (St.) intermedium (auct.) (top Ac. (St.) prorsum Zone), transitional forms between Pr. kockeli and Pr. kuehni (?S. (Eo.) sulcata s.l./Pr. kuehni Zone), reworked Bi. costatus and Pa. gracilis gracilis, and Liobolina sp. 1; ?Upper Crisis Interval III.

Lower Stockum Limestone, Bed 1 and 1/2 (= 13d) with Ac. (Str.) carinatum (upper Ac. (St.) prorsum Zone), Pr. kockeli, Po. purus subplanus, Polygnathus ?n. sp., and Cryptotaxis culminidirectus (upper part of Pr. kockeli Zone), Belgibole abruptirhachis abruptirhachis, Macrobole, reworked Liss. wocklumeri and (perhaps) Post. evoluta, ?minor transgression, local Upper Crisis Interval IIc.

Base of Bed 1, laterally discontinuous reworking level with re-sedimented Wocklumeria, Pa. gracilis ssp., Ps. marburgensis trigonicus, Bi. costatus, Bi. ultimus ultimus, ostracods and trilobites, ?regressive phase, local Upper Crisis Interval IIb.

Stockum Level Black Shale: Beds 96–100, local lenticular unit of black shale with black limestone nodules and conodonts of the Protognathodus Biofacies.

Beds 99–100 with Post. evoluta, Post nigra, and Ac. (St.) cf. prorsum (upper Ac. (St.) prorsum Zone), with Pr. kockeli (lower part of Pr. kockeli Zone), local Upper Crisis Interval IIa.

Beds 96–98 with Post. evoluta and Post. nigra (middle Ac. (St.) prorsum Zone) and impoverished Pr. meischneri-Pr. colllinsoni Fauna (upper ckI), initial post-glacial transgression, Upper Crisis Interval I.

Hangenberg Sandstone:

Bed 95, thin- to slightly cross-bedded, fossiliferous, pyritic, micaceous, lenticular siltstone with Ac. (St.) cf. procedens and Ac. (St.) cf. prorsum (lower Ac. (St.) prorsum Zone, UD VI-F), no conodonts (middle ckI), important regression (high Zr/Al ratio), with sequence boundary at the sharp, discontinuous base, Middle Crisis Interval II.

Hangenberg Black Shale:

Bed 94, 40 cm organic-rich, black, fissile alum shale, poor in macrofauna but with rare Post. cf. evoluta, base of Post. evoluta Zone (UD VI-E) and lower ckI (no conodonts so far), maximum flooding (low Zr/Al ratio), anoxic (high U/Th ratios), Lower Crisis Interval II.

Main Hangenberg Extinction of ammonoids and conodonts at the somewhat gradual base, Lower Crisis Interval I.

Wocklum Limestone: Strongly cyclic alternation of grey, nodular mudstones/wackestones and calcareous shales:

Bed 93, last three nodules layers (7–10 cm), dark-grey, pyritic, with Epi. applanata, the last W. denckmanni (Figs. 5a–b), P. paradoxa, F. wocklumensis, Cyrtoclymenia, May. nucleus, and Ebbighausenites (Epi. applanata Subzone, UD VI-D2), the last Bi. costatus, Bi. ultimus ultimus, Ps. marburgensis trigonicus, and Pa. gracilis ssp., Rabienops horni, ?Cryphops wocklumeriae, and Chaunoproetus stockumensis; minor deepening, Crisis Prelude II.

Bed 92, local, 30–40-cm thick, lenticular “Drewer Sandstone”, a pyritic, calcareous and micaceous, laminated siltstone, type level of Post. evoluta, regressive phase, Crisis Prelude I.

Bed 91 with W. denckmanni and W. sphaeroides (W. denckmanni Zone, UD VI-D1).

Samples 3–5 (Korn et al. 1994) with P. paradoxa and Glatziella glaucopis (P. paradoxa Subzone, UD VI-C2).

Sample 1 (Korn et al. 1994) with Gl. cf. minervae and Gl. glaucopis (M. galeata to P. paprothae Zones, UD VI-A2 to C1).

In the 1978 section of Clausen et al. (1989a), the top of the Wocklum Limestone is followed by a bed (Sample 7) with mixed, dominant pre-crisis conodonts and a single Pr. kockeli. The next bed (Sample 6) had already S. (S.) bransoni. Therefore, the critical DCB interval was missing by extreme condensation. The situation was not much better in their section sampled in 1979.

Discussion: Drewer is the only Rhenish section, where the shallowing upwards in the upper Wocklum Limestone led to a siltstone intercalation, the “Drewer Sandstone”, which is a good marker for the base of the Crisis Prelude. The Middle Crisis Interval is locally very condensed, possibly due to an unconformity at the base of the silty equivalent of the Hangenberg Sandstone. Therefore, there is locally no Hangenberg Shale. The lateral disappearance of several units, for example of the Hangenberg Black Shale, Drewer, and Hangenberg Sandstones, reflects a steep palaeoslope. Due to increasing turbulence upslope, siliciclastics did not settle towards the top of the seamount. The reworking in the Upper Crisis Interval, within the Pr. kockeli Zone, either reflects a minor regression or was the result of local synsedimentary tectonics, which triggered slumping. Glide folds are well-developed higher in the Carboniferous (Kronberg et al. 1960).

GSSP Prospects: Drewer would be a prime GSSP candidate if the DCB was defined by the Hangenberg Black Shale. For a higher boundary, its advantages are a thick and complex Upper Crisis Interval. Its main disadvantages are the lateral pinching out of beds, the inaccessibility of the Stockum Level Black Shale and its important limestone nodules in the vertical quarry wall, and the scarcity of conodonts in the critical units. Above the Wocklum Limestone, many conodont taxa tend to be represented in normal-sized samples by single specimens only (see tables in Clausen et al. 1989a). Therefore, it is hardly possible to study morphological changes within protognathids above the Hangenberg Sandstone. Apart from the top Wocklum Limestone, ammonoids are also rare.

Kattensiepen (Fig. 7)

Location: Variably active quarry at the road from Rüthen to Suttrop, topographic sheet 4516 Rüthen, r 3 457 980/h 5 703 750, northern limb of Warstein Anticline (Fig. 9; asymmetric Kattensiepen Anticline).

Literature: Staschen (1968), Struckmeier (1974), Stoppel 1977, Heuser et al. (1977), Clausen and Leuteritz (1979b), Clausen et al. 1984b), Luppold et al. (1994), Korn (2002, 2017), Koch et al. (2003: type locality of the arthropod Suttropcaris bottkei), Slotta et al. (2011).

Summary of succession: The Famennian to basal Carboniferous consist of ca. 60 m, very strongly cyclic, well-bedded nodular limestone. Only the Annulata Event beds are rich in macrofauna, especially in ammonoids. Based on logging by H. Uffenorde, the DCB succession includes:

Belecke Member of Eichenberg Formation: 2.5 m dark-grey shale with phosphatic nodules, especially at the base and above a short outcrop gap.

Hangenberg Limestone: 70 cm middle-grey, nodular, argillaceous limestone with S. (Eo.) sulcata s.l./Pr. kuehni, Ps. triangulus inaequalis, and Ps. triangulus triangulus Zones in succession, post-Crisis Interval.

?Stockum Limestone: 40 cm silty limestone.

Hangenberg Sandstone: 58 cm grey, calcareous, micaceous siltstone, Middle Crisis Interval II.

Hangenberg Shale: 17 cm silty shale, Middle Crisis Interval I.

- short outcrop gap –

Wocklum Limestone: Nodular and flaserlimestone.

Discussion: Luppold et al. (1994) note that the strongly condensed DCB interval is represented by siliciclastics without macrofauna and relevant conodonts. Unconformities (gaps) are likely and the tectonic deformation is strong. This excludes the quarry from further DCB discussions.

Bilstein Cave

Location: Old shooting exercise ground 400 m SE of the entrance to the Bilstein Cave, ca. 3 km SW of Warstein, topographic sheet 4516 Warstein, r 3 453 210/h 5 698 930 (Fig. 9).

Literature: Sandberger (1853), Schmidt (1922, 1924a, b), Paul (1939b; type-region of Pterochaenia schmidti), Richter and Richter (1949), Clausen et al. (1979), Korn (1981a), Clausen et al. (1984b), Luppold et al. (1994), Korn et al. (2016).

Succession: This DCB succession is strongly tectonised, silicified, and incomplete. It yielded important upper/uppermost Famennian ammonoids (type locality of C. warsteinensis Korn in Clausen et al. 1979, and C. nephroides Korn, 1981a). Since there is a significant unconformity above the Wocklum Limestone, the section is irrelevant for the current DCB discussion.

Eulenspiegel (Fig. 7)

Location: Middle to uppermost Famennian nodular limestones of a special saddle (Eulenspiegel Anticline), reaching ca. until UD VI-B/C, were exposed in an old quarry at the old road from Kallenhardt-Heide to Rüthen (topographic sheet 4516 Warstein, r 3 461 370, h 5 704 120; Fig. 9). The DCB became episodically accessible ca. 150 m to E, along the western slope, when a new road from Rüthen to Nuttlar was built. This outcrop is now grown over.

Literature: Schmidt (1922, 1924a, b), Richter and Richter (1926: type locality of Waribole eulenspiegelia), Paul (1939b), Clausen and Leuteritz (1979a, b), Clausen et al. (1984a, b), Clausen et al. (1987, 1989a), Luppold et al. (1994), Sartenaer (1997).

Succession (based on Clausen et al. 1989a and Luppold et al. 1994):

Kahlenberg Formation: Ca. 1.3 m Lower Alum Shale, in the upper part with phosphorite concretions, Lower Alum Shale Event Interval, middle Tournaisian.

Hangenberg Limestone: Strongly condensed flaserlimestones.

- ?minor unconformity (upper Hangenberg Limestone, S. (S.) sandbergi Zone) -

Bed 24, ca. 25 cm flaserlimestone with S. (S.) mehli, S. (S.) duplicata, S. (S.) bransoni, S. (S.) cf. wilberti (“duplicata sensu Hass”), S. (S.) carinthiaca, and Ps. triangulus inaequalis (S. (S.) mehli Zone) -

Bed 23, ca. 30 cm, thick-bedded flaserlimestone with S. (S.) bransoni, S. (Eo.) sulcata s.l., and others (S. (S.) bransoni Zone).

Bed 22, ca. 15 cm flaserlimestone with Pr. kuehni, Pr. kockeli, Pr. collinsoni, Pr. meischneri, S. (Eo.) sulcata s.l., Ps. dentilineatus (= Ps. primus primus), Po. purus purus, and others (S. (Eo.) sulcata s.l./Pr. kuehni Zone), post-Crisis Interval.

- ?minor unconformity (Upper Crisis Interval III) -

Stockum Limestone:

Bed 21, 10 cm flaserlimestone with Pr. kockeli, S. (Eo.) praesulcata s.l., Po. purus subplanus, Po. inornatus, bispathodids, and Neo. communis communis (Pr. kockeli Zone), Lower Stockum Limestone, Upper Crisis Interval II.

Bed 20, ca. 12 cm shale.

Beds 18/19, two layers of limestone nodules, not sampled for conodonts, possibly Basal Stockum Limestone, Upper Crisis Interval I.

Hangenberg Shale/Sandstone: Bed 17, ca. 60 cm silicified, hard, calcareous shales and siltstones, Middle Crisis Interval.

Hangenberg Black Shale: Bed 16, ca. 25 cm black shale with small Guerichia, Lower Crisis Interval.

Wocklum Limestone:

Ca. 1.1 m well-bedded, dark-grey flaserlimestone with very thin shale interbeds, poor in macrofauna.

Bed 15 with Wocklumeria sp. (W. denckmanni Zone, UD VI-D) and the last Bi. ultimus ultimus (including Bi. ziegleri), Ps. marburgensis trigonicus, Pa. gracilis (three subspecies), and with Pr. meischneri (top S. (Eo.) praesulcata s.l. Zone), ?Crisis Prelude.

Beds 12–14 with Ps. marburgensis trigonicus and rare Bi. ultimus ultimus, without siphonodellids (higher Si. (Eo.) praesulcata s.l. Zone), pre-Crisis Interval.

Bed 11 with Po. inornatus and S. (Eo.) prasesulcata s.l. (Si. (Eo.) praesulcata s.l. Zone).

Beds 5–10 with Bi. ultimus ultimus, Pa. gracilis gonioclymeniae, and Ps. marburgensis trigonicus (Bi. ultimus ultimus Zone), uppermost Famennian.

Discussion: The section was of special importance since it showed the joint entry of Pr. kuehni and S. (Eo.) sulcata s.l. in Bed 22. However, the dominance of siphonodellids in that bed clearly place it in the basal Hangenberg Limestone, whilst there is no protognathodid succession within the locally condensed Stockum Limestone.

Scharfenberg (Fig. 7)

Location: Former small quarry and slope on the eastern side of the road from Scharfenberg to Brilon, NE Sauerland (Fig. 9), topographic sheet 4517 Alme, r 3 467 670/h 5 698 630.

Literature: Matern (1929), Paeckelmann and Kühne (1936), Stoppel (1977), Clausen et al. (1989a), Luppold et al. (1994).

Succession: The following summary is mostly based on Clausen et al. (1989a):

Kahlenberg Formation (Lower Alum Shale): Black shale, Lower Alum Shale Event Interval, middle Tournaisian.

Hangenberg Limestone: Ca. 1.5 m alternation of 11 grey to light-grey, partly argillaceous, nodular limestone beds and layers of limestone nodules with grey to dark-grey silty shales, poor in macrofauna.

Beds 12–14 with S. (S.) obsoleta, S. (S.) lobata, S. (S.) quadruplicata, and S. (S.) cooperi (probably S. (S.) lobata M1 Subzone).

Beds 10–11 with S. (S.) mehli, S. (S.) carinthiaca, Ps. triangulus inaequalis, and other conodonts (main S. (S.) mehli Zone).

Beds 8–9 with “S. duplicata sensu Hass” (= S. (S.) cf. wilberti) (lower S. (S.) mehli Zone).

Bed 7 with S. (S.) duplicata, S. (S.) bransoni, and other conodonts (S. (S.) duplicata Zone).

Bed 6 with S. (S.) bransoni and S. (Eo.) sulcata s.l. (S. (S.) bransoni Zone).

Beds 4–5 with Pr. kuehni, Pr. kockeli, abundant Ps. dentilineatus (= Ps. primus primus), and S. (Eo.) sulcata s.l. (S. (Eo.) sulcata s.l./Pr. kuehni Zone), post-Crisis Interval.

Stockum Limestone:

Beds 1–3, ca. 50 cm alternation of four grey to dark-grey limestone beds and grey or greenish-grey silty shales, with Pr. kockeli, Pr. collinsoni, Pr. meischneri, Po. inornatus, and Po. purus subplanus (in Bed 3), Pr. kockeli Zone with high Protognathodus frequency, Upper Crisis Interval II.

Hangenberg Shale: Ca. 150 cm olive-grey to greenish-grey, silty shales, Middle Crisis Interval.

Hangenberg Black Shale: Ca. 10 cm black shale, Lower Crisis Interval.

Wocklum Limestone equivalents (no modern formation name): Olive to greenish-grey shales without macrofauna, pre-Crisis Interval to Crisis Prelude.

Eastern Münsterland subsurface

Vingerhoets 93 Well near Oelde (Fig. 7)

Location: Topographic sheet 4115 Rheda-Wiedenbrück, r 3 442 850, h 5 644 880, 40 km NNW of Drewer, ca. 1 km NNE of Oelde. The location has been assigned to the surfacing NE end of the Bochum Syncline.

Literature: Bless et al. (1976), Clausen (2008: map with precise position).

Succession: The DCB succession drilled in the Vingerhoets 93 Well has only very briefly been published but it is remarkable because the Hangenberg Black Shale with Post. evoluta has been penetrated:

“Upper Hangenberg Formation s.l.” (Stockum to Hangenberg limestone equivalents):

Above 1680.6 m, dark-grey shales with a few beds of silty limestone.

1680.6–1691 m, dark shales with thin beds of silty limestone with Ac. (St.) intermedium (auct.), Upper to post-Crisis Interval.

Hangenberg Shale/Sandstone:

1691–1700 m, dark shale, cherts, and siltstones; upper part of Middle to Upper Crisis Interval.

1700–1716 m, dark shales, siltstones, and partly calcareous sandstones with chonetids and tabulate corals, neritic Middle Crisis Interval.

Hangenberg Black Shale:

1716–1720 m, black, cherty shale with Post cf. evoluta (reported as C. euryomphala), UD VI-E, transgressive Lower Crisis Interval.

Un-named Formation (proposed name: Vingerhoets Formation):

1720–1734.6 m, quartzitic, partly calcareous sandstone, pre-Crisis interval to Crisis Prelude.

Discussion: Further to the S, DCB beds were also reached by the Anröchte Well (4415/1001, Dölling and Piecha 2010, sheet 4415 Anröchte, r 3 449 455, h 5 712 859). Equivalents of the Wocklum Limestone could be proven by a conodont sample with Pa. gracilis gonioclymeniae. However, there was no evidence for the Hangenberg Black Shale above, and all of the Crisis Interval and lower Tournaisian (Hangenberg Formation) are represented by unfossiliferous grey shale and siltstone. The Lower Alum Shale Event could be recognised by a change to dark-grey to black shales.

Attendorn-Elspe Syncline (central Sauerland)

The section at Trockenbrück described by Kronberg et al. (1960) is tectonically too complex and too incomplete to be re-considered here.

Grimminghausen

Location: Track slopes N of the village zur Sange, Grimminghausen region, Elspe Syncline, central Sauerland (Fig. 9), sheet 4713 Eslohe, r 3,444 920, h 5 676 520. Luppold et al. (1994) mentioned a new adjacent outcrop created during excavations for a garage but details of their complete logging of the Hangenberg Limestone were not published subsequently.

Literature: Weber (1934), Rabien (1954, 1960: type locality of Richterina (Richt.) robusta), Streel (1969: failed attempt to retrieve useful miospore assemblages), Ebert and Müller (1973), Clausen et al. (1994).

Succession: The combined evidence from the literature is as follows:

Kahlenberg Formation (Lower Alum Shale): 25–30 m dark-grey to black, thin-bedded shale/alum shale, in the upper part cherty, Lower Alum Shale Event Interval, middle Tournaisian.

Hangenberg Limestone: 4.8 m, 30 individual beds of hard, grey, poorly fossiliferous, often lenticular/nodular limestone, at the top with G. crassa, Ac. (St.) cf. intermedium (auct.) (“G. crassa Zone”, LC I-C/D), and Richterina (R.) robusta (type level), post-Crisis interval.

Hangenberg Shale s.l.: Grey shales with abundant ostracods (Richt. (Richt.) striatula) and guerichiids, allegedly also with a last phacopid; undifferentiated Crisis Interval.

Wocklum Limestone equivalents:

15 m grey shale and few, thin limestone beds with abundant ostracods (Richt. (Richt.) striatula, Maternella (Mat.) hemisphaerica, and others, M. (Mat.) hemisphaerica-M. (Mat.) dichotoma Zone) and trilobites (Silesiops schindewolfi, Weyerites wocklumeriae, Dianops, Chaunoproetus palensis), upper pre-Crisis Interval to Crisis Prelude.

15 m grey shales and nodular limestone with Wocklumeria sp., May. nucleus, prionoceratids (W. denckmanni Zone, UD VI-D), Drevermannia schmidti, Maternella (Mat.) hemisphaerica, and other ostracods, pre-Crisis Interval.

Taxonomic notes (RTB)

Siphonodella (Siphonodella) lobata (Branson and Mehl, 1934) Morph 2

1959 Siphonodella lobata—Voges: pl. 35, fig. 39 (only).

1966 Siphonodella lobata—Klapper: pl. 2, figs. 2–3 (only).

1985Siphonodella (Siphonodella) lobata—Ji: pl. 3, figs. 11–12 (only).

1985Siphonodella lobata—Ji et al.: pl. 20, figs. 9, 10–11, 14, pl. 21, figs. 13–20 (only).

1989 Siphonodella (Siphonodella) lobata—Ji: pl. 14, figs. 3a–b, 4a–b.

2017 Siphonodella lobata—Kaiser et al.: figs. 10.6 and 10.13 (only).

Definition: Morphotype of S. (S.) lobata with an only incipient side lobe of the platform, which lacks a secondary carina at maturity on the oral surface.

Stratigraphic range: Lower Tournaisian, S. (S.) mehli to S. (S.) sandbergi Zones.

Gattendorfia involuta Schindewolf, 1924 (emend.)

*1924 Gattendorfia involuta nov. sp.—Schindewolf, p. 105

1924 Gattendorfia n. sp.—Schmidt, p. 151

1926 Gattendorfia involuta—Schindewolf, p. 94

*cf.1952 Gattendorfia tenuis n. sp.—Schindewolf, pp. 297–298, text-fig. 18, pl. 3, figs 1a–1b (holotype)

1960 Gattendorfia tenuis—Vöhringer, p. 153, text-figs 28–29, pl. 5, figs 6a-6b (neotype of G. involuta)

cf.1965a Gattendorfia tenuis—Weyer, pp. 447–448, pl. 6, figs 1a–1b (further synonymy)

1972 Gattendorfia tenuis—Weyer, p. 342

cf.1977 Gattendorfia tenuis—Weyer, p. 173, pl. 1 figs 2–3

cf.1986 Gattendorfia tenuis—Bartzsch and Weyer, pl. 2, fig.2

1994 Gattendorfia involuta—Korn, p. 71

1994 Gattendorfia tenuis—Korn, p. 75, figs 65B, 66E-H, 67D, 68B

Type: The original of G. tenuis in Vöhringer (1960: pl. 5, figs 6a–6b), Tübingen Collection, no. 1130/91, is here selected as the neotype. Its suture has been illustrated by Vöhringer (1960: fig. 38) and Korn (1994: fig. 67D).

Discussion: Attached to a discussion of his new genus Paragattendorfia, Schindewolf (1924) briefly introduced two new species of Gattendorfia. His Gattendorfia involuta was explained to differ from the type species of the genus (G. subinvoluta) by its more compressed and more narrowly umbilicated conch shape with higher whorls. This brief cha-racterisation was sufficient at the time (before 1931) for a valid species definition (see Article 12 of the Code for Zoological Nomenclature). Statements in Weyer (1965a, 1972) and Korn (1994) that G. involuta is a nomen nudum are unjustified. Possibly influenced by Richter (1948; see discussion in Weyer 1972, p. 340), who wrongly advocated that an illustration was mandatory for a valid species definition, Schindewolf (1952, p. 298) assumed himself that his “third Gattendorfia species” from 1924 did not yet have a valid name. Therefore, he re-described it as G. tenuis, not mentioning at all his given name from 1924. He further stated that his previously available well-preserved specimens from Oberrödinghausen and Silesia, the involuta syntypes, had been lost. Therefore, he selected a specimen collected by Schwan from Gleitsch, Thuringia, as the holotype of G. tenuis (Tübingen collection Ce 1012/37). The neotype of G. involuta selected here is a well-preserved specimen from one of the two type localities (Oberrhödinghausen). Vöhringer (1960) and Korn (1994) illustrated several cross-sections of G. involuta topotypes (as G. tenuis), which enable a morphometric characterisation. Gattendorfia tenuis is a subjective junior synonym since it is based on a form from Thuringia, not from the Rhenish Massif. Its previously assumed identity with G. involuta has to be tested by investigations of ontogenetic morphometry. Two early whorl cross-sections of G. tenuis, illustrated by Weyer (1977) from the Schleiz region of Thuringia, suggest a gradual change from broadly depressed to higher whorls during the fifth whorl, possibly earlier than in typical G. involuta (during the 7th whorl in the involuta topotype Ce 1130/176, illustrated by Vöhringer 1960 and Korn 1994). This may reflect intraspecific variability but more morphometric data are required to solve the question.

The new specimen illustrated in Fig. 15 is the so far oldest representative of the species from the basal G. subinvoluta Subzone (base of Bed 6a at Oberrödinghausen, G. subinvoluta Subzone, LC I-A2). It suggests that G. involuta belonged to the root stock of the Gattendorfiinae.

Fig. 15
figure15

Gattendorfia involuta, new typical, convolute specimen from the base of Bed 6a (G. subinvoluta Subzone, LC I-A2, base of true Hangenberg Limestone) of the Oberrödinghausen Railway Cut, lateral view (incomplete preservation prevents a meaningful ventral view), B6C.54.11, × 1

A currently incomplete knowledge of morphology and distribution patterns is not only true for the pair G. involuta-G. tenuis. It also applies to G. subinvoluta, which holotype and a topotype from Gattendorf, Franconia (see Frech 1902; Schindewolf 1923a; Korn 1994), lack the constrictions that are well developed in Rhenish representatives figured by Vöhringer (1960), Korn (1994, 2006), Korn and Weyer (2003), and here (Fig. 3l, m). However, Vöhringer (1960, p. 151) noted that constrictions are absent in some specimens from Oberrhödinghausen and R. Richter collected in 1925 an adult from there (housed in the Senckenberg collection, Frankfurt a.M.) that has no constriction in the last ca. 250° of the last whorl at 72 mm diameter. This suggests ontogenetic changes, with increasing spacing of constrictions towards maturity. Thuringian G. subinvoluta illustrated by Bartzsch and Weyer (1982) also lack prominent constrictions, which supports a possible difference between Rhenohercynian and Saxothuringian populations. These were biogeographically separated in the basal Carboniferous by a narrow oceanic system.

Conclusions

  1. 1.

    The Rhenish Massif is one of the most important classical regions for DCB research, which successions set the standards for conodont, ammonoid, and event stratigraphy. A large part of the data was published only in regional journals or in German. Therefore, the initiative of this special issue to summarise internationally the DCB knowledge is a good opportunity to make this information better available.

  2. 2.

    The uppermost Famennian to basal middle Tournaisian interval can be subdivided into ten conodont zones, which are mostly defined by the FADs of species. As an exception, one zone, the costatus-kockeli Interregnum, is defined by the global extinction (LADs) of important taxa, such as Bi. costatus and Bi. ultimus (all subspecies), Ps. marburgensis trigonicus, and the last palmatolepids (all subspecies of Pa. gracilis, assuming a reworked nature of rare post-Hangenberg Extinction records).

  3. 3.

    The poor definition and ongoing revision of the oldest siphonodellids require to add currently the phrase s.l. (sensu lato) to identifications as S. (Eo.) praesulcata and S. (Eo.) sulcata. The type of S. (Eo.) praesulcata originated from a level above the main Hangenberg Extinction. It is likely that the most common and stratigraphically most useful pre-extinction siphonodellid will receive in future a different species name, with implications for zonal nomenclature. It is also possible that the use of the name S. (Eo.) sulcata eventually will be restricted to forms close to its lost holotype.

  4. 4.

    Due to large taxonomic uncertainties concerning S. (S.) jii, it is better to return to the original definition of the Upper duplicata Zone in the lower Tournaisian, resulting in a re-naming as S. (S.) mehli Zone. It replaces the S. (S.) jii Zone of Becker et al. (2016). Siphonodella (S.) carinthiaca and S. (S.) cooperi (M2 or s. str.) are important additional marker taxa entering in the same zone. Lower Tournaisian forms from the Rhenish Massif that were previously identified as S. duplicata sensu Hass are preliminarily assigned to S. (S.) cf. wilberti, until the variability of the middle Tournaisian species S. (S.) wilberti is fully established.

  5. 5.

    The S. (S.) sandbergi Zone is subdivided into successive S. (S.) sandbergi and S. (S.) lobata M1 subzones. The new, morphologically less advanced S. (S.) lobata M2 enters significantly earlier. The Rhenish siphonodellid record questions a subdivision of the S. (S.) sandbergi Zone based on the FAD of S. (S.) quadruplicata, at least unless ranges of early (M2) and typical forms (M1) of the latter are fully established.

  6. 6.

    More data are required to correlate the FADs of Ps. triangulus inaequalis and Ps. triangulus triangulus precisely with the siphonodellid succession.

  7. 7.

    The uppermost Famennian to top lower Tournaisian of the Rhenish Massif can be subdivided into a dozen ammonoid zones, with four additional subzones. New are the May. nucleus Subzone (UD VI-C3), an upper subdivision of the former P. paradoxa Subzone/Zone, the “Eoc.nodosus Subzone (LC I-A3), an upper subdivision of the G. subinvoluta Zone, and the Parag. sphaeroides Subzone (LC I-B2), an upper subdivision of the Pap. dorsoplanus Zone.

  8. 8.

    Based on litho- and conodont stratigraphy, a succession of Ac. (Stockumites) faunas can be recognised within the Ac. (St.) prorsum Zone, which straddles the DCB. However, the evidence, often from different outcrops, is still insufficient to enable a subzone subdivision.

  9. 9.

    The extended Hangenberg Crisis is formally subdivided into a regressive Crisis Prelude (top S. (Eo.) praesulcata s.l. Zone, UD VI-D2, “Drewer Sandstone” and top Wocklum Limestone, HST), transgressive Lower Crisis Interval (lower costatus-kockeli Interregnum, UD VI-E, HBS, TST, with the main pelagic extinction at the base, regressive Middle Crisis Interval (upper costatus-kockeli Interregnum, main UD VI-F, with a sequence boundary between the HS, a FSST, and the HSS, a LST), transgressive Upper Crisis Interval (Pr. kockeli Zone to lower part of S. (Eo.) sulcata s.l./Pr. kuehni Zone, top UD V-F/LC I-A1, Stockum Limestone and lateral black shales/marls, TST with parasequences), and subsequent basal Carboniferous post-Crisis Interval (Hangenberg Limestone, HST). Terrestrial extinctions (top of LN Zone) and obviously also the extinction of various neritic fossil groups occurred high within the Upper Crisis Interval. The bases of the Pont d’Arcole Formation (in neritic western settings) and Lower Alum Shale (in the deeper, eastern Kulm facies) mark a sudden flooding (TST base) that defined the classical middle Tournaisian (Tn 2).

  10. 10.

    The west-east transition from neritic to pelagic facies and faunas enables the correlation of shallow and deep shelf environments. The selection of the best/most significant sections led to a review of 30 successions, from the Aachen region in the west, through sections along the Velbert and Remscheid-Altena Anticline (Bergisches Land to northern Sauerland), to the eastern Sauerland (Warstein region), the subsurface to the north, and the Attendorn-Elspe Syncline in the central Sauerland. Unfortunately, more than half of the sections were temporary (bore holes, roadwork exposures, trenches) or have been destroyed subsequently and are not available any more for research. Further ten sections include outcrops gaps or unconformities near the DCB, which excludes them for the current search for a new DCB GSSP.

  11. 11.

    The Apricke section has only insufficiently been studied so far and requires moderate excavations for further investigations. The important Oese and Drewer sections are poor in conodonts in the Upper Crisis Interval but represent important auxiliary sections, wherever the future GSSP will be placed. The currently best Rhenish section at the Borkewehr or Burgberg near Wocklum is regarded as a GSSP candidate. Many new data will be presented in a forthcoming separate manuscript that will submitted soon to this journal.

  12. 12.

    The complete set of reviewed sections and different facies developments recommends the Rhenish Massif as a package of auxiliary sections, in which a future GSSP would be embedded.

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