Introduction

Quarries are areas of pivotal importance for investigation, popularization, and educational purposes in the field of geosciences (Gajek et al. 2019; Prosser 2018, 2019). Indeed, quarries represent privileged “windows” onto the geology of a given area, allowing for the analysis of exposures that would otherwise be hidden by vegetation, soil, or buildings (Margiotta and Sansò 2017). Therefore, although quiescent and abandoned quarries are often regarded as degraded areas, they can prove very valuable sites for research, geotourism, and teaching even after the dismissal of quarrying activities (English Nature et al. 2003; Prosser 2003, 2018; Prosser et al. 2006; Thompson et al. 2006; López-García et al. 2011; Henriques and Dos Reis 2015; Margiotta and Sansò 2017; Mata-Perelló et al. 2018; Meléndez 2018; Parkes and Gatley 2018; Zoboli and Pillola 2021; Zoboli et al. 2021).

Quarries where sedimentary rocks or loose sediments are extracted are of particular relevance for paleontology as the quarrying activities may lead to discovering fossils that are preserved entombed in more or less lithified deposits. In addition, the discovery of huge amounts of fossils in a limited outcrop area such as a quarry (Zoboli et al. 2021) may allow for detailed reconstructions of ancient biocoenoses and paleoecosystems. Not least, if extraction affects a thick stratigraphic succession, paleobiological and paleoenvironmental variations may also be traced with accuracy through time.

Several prominent paleontological localities were discovered thanks to quarrying activities, including Holzmaden (Hess 1999; Smith and Vincent 2010) and Solnhofen (Barthel 1970) in Germany, the Strawberry Bank in England (Williams et al. 2015), and the Mygatt-Moore quarry of the USA (Mygatt 1991). Italian quarries of foremost importance for paleontology are, for instance, those of Besano (Lombardy, northern Italy) (Beardmore and Furrer 2019; Bindellini et al. 2021), of Baccinello (Tuscany, central Italy) (Harrison and Harrison 1989; Rook et al. 1996) and several that are located in the Salento Peninsula (Apulia, southern Italy) (Bianucci and Varola 2014; Peri et al. 2022). Depending on different quarry typologies, fossils can be discovered in different ways. In lithified rocks such as calcarenites, finds usually happen while saw-cutting rock blocks into slices (e.g., Bianucci et al. 2019a), whereas in poorly cemented deposits (e.g., clays and sands) fossils can be unburied accidentally during the quarrying operations themselves. Many areas of extraction of unlithified sediments where vertebrate fossil remains have been found occur all along the Italian Peninsula. The sediments extracted therein typically consist of sands and clays used in construction and for industrial purposes. Mostly referred to the Miocene and Pliocene epochs, these deposits are common at the foot of the Northern Apennines, in the Piedmont, Emilia-Romagna, and Tuscany regions. Vertebrate fossils that have been discovered at these locations mainly belong to marine groups (fishes, reptiles, and mammals), and subordinately to terrestrial vertebrates (reptiles and mammals). A relevant example is the Campore quarry (Parma Province, Emilia-Romagna), where three cetacean skeletons belonging to two delphinids and one balaenopterid were collected from Pliocene clays (Bianucci 1997; Freschi and Raineri 2014).

First attested in the Bronze Age, the quarrying activities represent an important aspect of the cultural, economic, and social landscape of Tuscany. According to the last edition of the “Piano Regionale Cave” (i.e. Regional Quarry Plan; Regione Toscana 2019), in 2016 the Tuscan territory hosted 384 active quarries from which a total of ca. 4,657,000 m3 of geomaterials were extracted annually. The exploiting activities are mostly related to building rocks (60%) and, subordinately, to industrial materials (30%) and ornamental stones (10%, including the world-famous Carrara marble). According to national data (ISTAT 2020), Tuscany is the second Italian region in terms of abundance of active quarries. Even more abundant are the inactive and abandoned quarries, which in Tuscany number almost 2400. Regional and national laws exist for regulating and encouraging the valorization and rehabilitation of abandoned quarries to serve social purposes (Regione Toscana 2019).

Pliocene clays and sands cover almost one-quarter of the whole Tuscan area (Fig. 1), and most of the fossil vertebrate remains that were collected in Tuscany during the last two decades come from both active and inactive quarries from which those sediments are (or used to be) extracted. Some such finds comprise the type materials of previously unknown species or represent rare/unique records all over the Mediterranean region (e.g. Bianucci et al. 2019b; Collareta et al. 2020b, c, 2021b, d; Merella et al. 2021, 2022a). During the last few years, we have been monitoring some Pliocene quarries in order to detect and collect new fossils that may come to light due to extraction and/or natural erosion. To date, the resulting material has been studied only in part; other studies are currently ongoing, aiming at reconstructing a detailed stratigraphic and paleoenvironmental framework for the recovered fossil assemblages.

An important goal of our research is to preserve and promote the most relevant investigated quarries for conservational, educational, and geotouristic purposes. Three such quarries are the main target of the present study, namely, an active quarry in the Pisa Province (La Serra quarry), a temporarily inactive quarry in the Grosseto Province (Arcille quarry), and an abandoned quarry in the Florence Province (Certaldo quarry). Reporting on the remarkable paleontological heritage of these quarries and discussing how it could be further protected and valorized is our aim here.

Fig. 1
figure 1

Modified from Benvenuti et al. (2014)

Simplified geological map of Tuscany. Stars indicate the geographic position of the studied sites. Alb: Albenga Basin; Rib: Ribolla Basin; Mbam: Montebamboli Basin; BC: Baccinello-Cinigiano Basin; Vel: Velona Basin; SR: Siena-Radicofani Basin; VC: Valdichiana Basin; Cec: Cecina Basin; Rad: Radicofani Basin; Cas: Casino Basin; TF: Tora-Fine Basin; Vol: Volterra Basin; VE: Valdelsa-lower Valdarno Basin; VA: upper Valdarno Basin; C: Casentino Basin; FPP: Firenze-Prato-Pistoia Basin; M: Mugello Basin; G: Garfagnana Basin; MTH: Montespertoli-Tavarnelle high.

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Geological Framework

The Mio–Pleistocene “Neoautochtonous” successions of Tuscany (Pertusati et al. 1980; Bossio et al. 1993, 1998), were deposited in the framework of the continental collision that led to the rise of the Northern Apennines (e.g. DeCelles 2012; Benvenuti et al. 2014). In such a complex geodynamic scenario, Pliocene deposition occurred in the frame of high-frequency cycles of relative sea-level variation. The whole process was controlled by both tectonics and climate (Nalin et al. 2016; Dominici and Forli 2021).

The three quarries studied herein are located in two Tuscan Neogene basins, namely, the Valdelsa and the Baccinello-Cinigiano basins (Garassino et al. 2012; Sorbi et al. 2012; Benvenuti et al. 2014; Dominci et al. 2018; Dominici and Forli 2021) (Fig. 1). The former is a 25 × 60 km, NW–SE elongated extensional basin of central-western Tuscany. The Valdelsa Basin is filled with some 1000 m of continental and marine deposits, spanning chronostratigraphically between the Upper Miocene and the Lower Pleistocene (Benvenuti et al. 2014). The sedimentary infill of the Valdelsa Basin has yielded significant remains of terrestrial and marine vertebrates (e.g., Capellini 1905; Azzaroli 1977; Benvenuti and Dominici 1992; Dominici 1994; Bianucci 1996; Rustioni and Mazza 2001; Abbazzi et al. 2008; Danise and Dominici 2014; Dominici et al. 2018; Collareta 2020; Collareta et al. 2016, 2017, 2020a, b).

The Baccinello-Cinigiano Basin of southern Tuscany is an 8 × 18 km, N-S elongated structural depression filled with some 250 m of Upper Miocene to Pliocene, siliciclastic, continental and marine sediments, interbedded with lignite and freshwater carbonate deposits (Benvenuti et al. 2001, 2015). These nonmarine strata host a peculiar vertebrate assemblage that includes the insular primate Oreopithecus bambolii, thought to have evolved bipedalism independently from the hominines (e.g. Rook et al. 2006, 2011; Rook 2016; Pandolfi et al. 2022).

Results

The La Serra Active Quarry

Overview

Located within the San Miniato municipality (Pisa Province), the La Serra sand and clay quarry (geographic coordinates: 43°39′28″ N; 10°48′57″ E) consists of an active, open-air extractive area, measuring ca. 175 × 150 m (Fig. 2a). The quarry is easy to reach, but accession is regulated by the quarrymen. The Pliocene succession exposed therein can be included in the S6 Synthem identified in the Valdelsa Basin by Benvenuti et al. (2014) (Dominici et al. 2018). Garassino et al. (2012) have divided the ca. 25-m-thick stratigraphic succession exposed at La Serra into four informal stratigraphic units that may be regarded as facies associations (Collareta et al. 2020a, b). The bottom unit (“Unit 1” of Garassino et al. 2012) is comprised of interbedded sands and silts, and cross-stratified sands. Spectacular sedimentary structures, including large-scale cross-stratification and accumulations of soft clasts, are evident in outcrop (Fig. 3a,b). The invertebrate fossil content of “Unit 1” includes conspicuous shells of the freshwater bivalve Margaritifera sp. (Garassino et al. 2012). Invertebrate traces consisting of vertical and horizontal burrows are widespread along some stratal surfaces (Fig. 3c), whereas Teredolites isp. borings excavate the relatively abundant wood fragments (Fig. 3d). “Unit 2” is comprised of cross-stratified, coarsening upward sands. Fragmentary bones of turtles and abundant invertebrate remains (including both bivalves and gastropods) occur in these sands (Garassino et al. 2012). An alternation of silts and clays comprises “Unit 3.” In the upper part of this unit, two parallel, sub-horizontal shell beds are preserved. These horizons feature abundant gastropods and bivalve shells, some of which are preserved in life position. “Unit 4” consists of fossil-bearing clayey sands. This is the most fossiliferous unit of the succession. In this stratal package, several marine vertebrate fossil remains (e.g., elasmobranchs and bony fishes) have been found in association with ubiquitous invertebrate shells and an exceptionally rich decapod assemblage (Garassino et al. 2012; Pasini and Garassino 2012; Coletti et al. 2023). These deposits have also yielded the youngest record of the brachiopod Lingula? from the Mediterranean (Di Cencio et al. 2021). Although contrasting biostratigraphic data have been published about the succession exposed at La Serra (Garassino et al. 2012), its assignment to the Upper Pliocene (Piacenzian) appears as well-supported overall (Di Cencio et al. 2021, and references therein).

Fig. 2
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Panoramic views of the three studied quarries. a La Serra quarry. b Arcille quarry. c Certaldo quarry. All the photographs were taken with a DJI Mavik Pro drone

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Fig. 3
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Outcrop close-ups from the three investigated quarries. a Cross stratification at the La Serra quarry; b Accumulation of clay chips at the La Serra quarry; c Vertical burrow at the La Serra quarry; d Teredolites isp. perforating a carbonified wood fragment at the La Serra quarry; e Gutter cast at the Arcille quarry; f Interbedded conglomerates and sands at the Arcille quarry; g Thalassinoides-like network of subhorizontal burrows at the Arcille quarry; h Shell-rich bed at the Certaldo quarry

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Vertebrate fossils

Abundant remains of continental, freshwater, and marine vertebrates have been found at La Serra. Specimens from the lowermost “Unit 1” include exquisitely preserved carapacial and plastral bones of the freshwater turtle Mauremys sp. (Collareta et al. 2020a). Two small, oval traces were detected on this plastron; belonging to the rarely reported ichnotaxon Thatchtelithichnus holmani, these bone modifications suggest parasitization of the turtle by leeches (Zonneveld and Bartels 2022). Other freshwater and terrestrial turtle fossils are currently under investigation. Garassino et al. (2012) also recorded several indeterminate remains of turtles and cervids from this unit. The fossil content of “Unit 2” includes fragments of jaws as well as long bones of cervids, postcranial elements of proboscideans, and dentigerous bone fragments of suids (Luca Pandolfi, pers. comm.). All these specimens are currently under study (Fig. 4a). No fossil vertebrates are hitherto known from “Unit 3”. Several fish teeth and spines come from “Unit 4”. Two such remains were referred by Garassino et al. (2012) to an indeterminate carcharhinid taxon to the great white shark (Carcharodon carcharias). Dental remains belonging to the sand tiger shark (Carcharias taurus), an eagle ray species (Myliobatis sp.), and the tiger shark (Galeocerdo cuvier) were also found recently in this unit (Fig. 5a-c). A relevant discovery from this stratal package consists of the longest stingray stinger (a venomous spine located on the tail of myliobatoid rays) ever described from both the fossil and the recent records, which was tentatively referred to? Dasyatidae indet. (Collareta et al. 2020b; Fig. 4e). All the vertebrate fossils from La Serra are part of permanent exhibitions, or are stored, in Tuscan museums and research institutions. In particular, several of these fossils are housed at the Museo Geopaleontologico Scienze della Terra (GAMPS) at Badia a Settimo (Scandicci municipality, near Florence). Here, in a recently established exhibition room that highlights the scientific potential of the Tuscan Pliocene fossil record, many fossils from La Serra (including the giant myliobatoid tail spine and a partial skeleton of Mauremys sp.) are exposed. Some mammalian postcrania are exposed in another room at the GAMPS, whereas other terrestrial vertebrate fossils are currently stored in the Vertebrate Paleontology Lab of the Dipartimento di Scienze della Terra dell’Università di Pisa, pending to be prepared for a detailed study.

Fig. 4
figure 4

Examples of vertebrate fossil collection at the investigated localities. a Excavation of a proboscidean vertebra at the La Serra quarry; b Discovery of a giant-sized stingray stinger at the La Serra quarry; c A tiger shark (Galeocerdo cuvier) tooth at the Arcille quarry; d Partly excavated skeleton of aff. Makaira sp. at the Arcille quarry; e Partly excavated skeleton of the sirenian Metaxytherium subapenninum at the Arcille quarry; f Excavation of a mandible of the delphinid Hemisyntrachelus sp. at the Canonica outcrop, near Certaldo

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Fig. 5
figure 5

Elasmobranch fossil teeth from the three studied quarries. a, f Carcharias taurus; b Galeocerdo cuvier; c Myliobatis sp.; d Cosmopolitodus plicatilis; e Hexanchus griseus; g Carcharhinus brachyurus; h Carcharhinus limbatus; i Nebriimimus wardi (holotype); j Pachyscyllium distans, k Nebriimimus wardi (paratype). a–c from La Serra, d–i from Arcille, j–k from Certaldo. All scale bars equal 5 mm

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Paleoenvironmental Reconstruction

Based on stratigraphic and paleontological considerations, the sedimentary succession exposed at La Serra reflects deposition in deltaic, lagoonal, and shallow-marine settings (Garassino et al. 2012; Collareta et al. 2020a, b; Di Cencio et al. 2021). More in detail, according to Garassino et al. (2012), “Unit 1” represents an estuarine or deltaic environment with scattered swamps; “Unit 2” reflects a barrier island with aeolian and submarine dunes; “Unit 3” was deposited in a brackish lagoonal context; and “Unit 4” testifies to a low-energy, offshore-transition, marine setting. The vertebrate finds are in broad agreement with this paleoenvironmental interpretation. Indeed, the Mauremys sp. remains from the first unit (Collareta et al. 2020a) suggest the nearby presence of freshwater bodies, whereas the occurrence of land mammals in “Unit 2” (Garassino et al. 2012) may testify to the fluvial transport of floating carcasses. The marine nature of “Unit 4” is confirmed by the taxonomic composition of the vertebrate assemblage, which includes sharks and rays belonging to essentially marine taxa (Garassino et al. 2012; Collareta et al. 2020b).

The Arcille Quiescent Quarry

Overview

The Arcille quarry (geographic coordinates: 42°47′1″ N; 11°17′03″ E) takes its place in the vicinities of Campagnatico (Grosseto Province). Although no extraction activities are currently ongoing at the site, access to the quarry is regulated by the owners. The Arcille fossil site is comprised of a quiescent sand quarry that develops along a 35-m-long, 100-m-high subvertical wall consisting of coarse- to fine-grained siliciclastic sediments. These deposits are part of the Neogene sedimentary infill of the Baccinello-Cinigiano Basin and belong to the Lower Pliocene S2 Synthem (as defined by Dominici et al. 2018). As reported in recent literature (e.g. Bianucci et al. 2019b; Collareta et al. 2021d; Dominici and Forli 2021; Merella et al. 2021, 2022a) the succession exposed at Arcille (Fig. 2b) consists of yellowish sandstones that alternate with conglomerates and are topped by grayish mudstones. The lower, sandy portion of the outcrop is home to most of the fossils that have been found at this site (see the following paragraph below). Impressive sedimentary structures, such as gutter casts (Fig. 3e) and conglomerate lenses (Fig. 3f) are present besides subhorizontal invertebrate burrows similar to Thalassinoides (Fig. 3g). In the uppermost sector of the sandy unit, two condensed horizons have also been recognized (see Tinelli 2013). In these levels, abundant vertebrate and invertebrate (mostly mollusks) remains have been recorded. The top of the outcrop is comprised of massive mudstones that entomb open-shelf bivalves and solitary ahermatypic corals (Dominici and Forli 2021). Biostratigraphic analyses of foraminifera assign the Arcille succession to the Zanclean (Sorbi et al. 2012), and in particular to the 5.08–4.53 Ma time span (Violanti 2012).

Vertebrate Fossils

The fossil assemblage from Arcille includes a huge amount of marine vertebrate remains belonging to cetaceans, sirenians, elasmobranchs, and bony fishes (Tinelli 2013; Bianucci et al. 2019b; Merella et al. 2020, 2021, 2022a; Collareta et al. 2021b). Five almost complete sirenian skeletons (Fig. 4b) were collected from the sandy portion of the succession and referred to the extinct dugongid Metaxytherium subapenninum (Sorbi et al. 2012; Tinelli et al. 2012). One of these exquisitely preserved skeletons is currently stored at the Museo di Storia Naturale dell’Università di Pisa (MSNUP), the others being permanently exposed at the GAMPS. Some sirenian bones are incised by shark bite marks, including some that have been left by bluntnose sixgill sharks (Hexanchus griseus) (Merella et al. 2021, 2022b); other feature the holotype and many referred specimens of the recently described ichnospecies Osteocallis leonardii (a probable polyplacophoran grazing trace) (Collareta et al. 2023). Both the currently known specimens of the extinct Mediterranean monodontid cetacean Casatia thermophila come from the same horizons as some of the sirenians (Bianucci et al. 2019b; Merella et al. 2022a). The holotype, in particular, consists of an incomplete but well-preserved skull that is currently exposed at the MSNUP, close to the skeletons of the two extant species of monodontids. The fish assemblage consists of more than three hundred dental and dermal remains (Bianucci et al. 2019b; Merella et al. 2020, 2022a; Collareta et al. 2021b) (Fig. 4c, 5d-i). The elasmobranchs account for about twenty species in the families Alopiidae, Carcharhinidae, Carchariidae, Dasyatidae, Hexanchidae, Lamnidae, Myliobatidae, Rajidae, Rhinobatidae, Scyliorhinidae, and Squatinidae. Highlights of this assemblage include the holotype of the recently described skate Nebriimimus wardi (Collareta et al. 2021b) and the first fossil teeth of the blacktip shark Carcharhinus limbatus from Europe and the whole Mediterranean area (Collareta et al. 2021d). As regard the bony fishes, two partial skeletons of billfish (aff. Makaira sp., Fig. 4d) were collected along with abundant teeth of labrid and sparid teleosts, and rarer otoliths (Tinelli 2013; Collareta et al. 2021d). Some selected elasmobranch and teleostean fossil specimens from Arcille are currently on exhibit at the GAMPS.

Paleoenvironmental Reconstruction

The Arcille quarry provides an unsurpassed reference for reconstructing the Early Pliocene marginal-marine paleoenvironments of Tuscany. Sedimentological considerations lead to reconstructing the depositional setting of the fossiliferous sands as a shallow-marine, coastal area prospicient to a river mouth (hence the conglomeratic strata). Moving up section, the grayish mudstones that cap the yellowish sands are indicative of a more distal, open-shelf depositional setting, thus suggesting a relative sea-level rise (Dominici and Forli 2021). The fossil assemblage is mainly comprised of shallow-dwelling, warm-water vertebrates, and invertebrates. Some of the detected species, such as the living tiger shark (Galeocerdo cuvier), bull shark (Carcharhinus leucas), and bull ray (Aetomylaeus bovinus) are powerful paleoenvironmental indicators, suggesting coastal waters and a warm paleoclimate. The extinct sirenian Metaxytherium subapenninum, for which dugong-like paleoecological habits have been proposed, further suggests closeness to a river mouth (Sorbi et al. 2012). Besides these quintessentially coastal species, several open-sea forms complete the marine vertebrate assemblage of Arcille, including the billfish (aff. Makaira sp.), the bluntnose sixgill shark (Hexanchus griseus) and the bigeye thresher shark (Alopias superciliosus), suggesting strong connections to open-sea paleoenvironments (Bianucci et al. 2019b; Merella et al. 2020). The latter feature may be explained by evoking a subsuperficial interface between the warm (thermospheric) and cool (psychrospheric) waters along the water column, an abrupt morphology of the seafloor, and the absence of physiographic barriers inhibiting faunal interchanges between the nearshore and open-sea environments (Merella et al. 2021). These peculiar environmental features allowed for the establishment of unusual paleoecological interactions, such as feeding by the deep-sea shark H. griseus upon the shallow-marine sirenian M. subapenninum (Merella et al. 2021, 2022b). From a paleobiological point of view, the recent discovery of Casatia thermophila is one of crucial importance for reconstructing the evolutionary history of monodontid cetaceans. Nowadays, the family Monodontidae is represented by the white whale (or beluga) and the narwhal, both these species being exclusive of the Arctic and Subarctic waters (Heide-Jørgensen 2018; O’Corry-Crowe 2018). The presence of monodontids in the Lower Pliocene deposits of Tuscany strongly supports a (sub)tropical origin for this family (Bianucci et al. 2019b).

The CertaldoAbandoned Quarry

Overview

This abandoned clay quarry (geographic coordinates: 43°34′08″ N; 11°01′51″ E) is located in the surroundings of the village of Certaldo (Florence Province). Here, fossiliferous deposits crop out along a ca. 90-m-long, 8-m-thick quarry wall that erodes in a badland-like fashion (Fig. 2c). Access to the quarry is not restricted, but the site has long been abandoned and dense vegetation covers all but the steepest surfaces. The deposits exposed in the quarry are part of the sedimentary fill of the Valdelsa Basin and mostly consist of massive, grayish-bluish, shelf mudstones (Collareta et al. 2021a) referred to the S3 Synthem (as defined by Benvenuti et al. 2014). The latter is mid-Pliocene in age, having deposited during the 3.98–3.19 Ma time span. Fossils concentrate in a ca. 25-cm-thick layer (Fig. 3h) occurring a few meters below the top of the exposed succession (Collareta et al. 2020c, 2021c). Most of the specimens consist of bivalves, gastropods, and barnacles (Collareta et al. 2020c). The quarry is part of a number of fossiliferous outcrops occurring in the close vicinities of Certaldo. Some 4 km East of the quarry, fossil-rich sands, and clayey sands crop out at the edges of a vineyard (Collareta et al. 2021c); here, remains of vertebrates and invertebrates (mostly mollusks) are concentrated in a handful of decimeter-thick horizons. A further fossiliferous site is that of “Canonica”, ca. 2 km northeast of Certaldo. It consists of silty clays that are exposed along small badlands (Alderighi et al. 2012). Both these additional outcrops are comprised of sediments belonging to the same S3 Synthem as the Certaldo quarry.

Vertebrate Fossils

The Certaldo quarry has recently been the location of the second unambiguous record of the extinct catshark Pachyscyllium distans in the Mediterranean Sea (Collareta et al. 2020c). Furthermore, the paratype of the skate Nebriimimus wardi also comes from these deposits (Collareta et al. 2021b) (Fig. 5j,k). Other elasmobranch teeth from the same sediments have been referred to Megascyliorhinus miocaenicus and Rostroraja sp.; in addition, bony fish otoliths can also be found at the Certaldo quarry. Relevant fossil finds from the nearby outcrops include a juvenile tooth of Aetobatus cf. cappettai, one of the latest representatives of the pelagic eagle rays (Aetobatidae) in the Mediterranean Sea (Collareta et al. 2021c), and an incomplete skeleton (including the fragmentary skull and mandibles) of the extinct delphinid Hemisyntrachelus sp. (Alderighi et al. 2012), which recent phylogenetic reconstructions relate to the extant killer whale Orcinus orca (Bianucci et al. 2022; Citron et al. 2022) (Fig. 4f). The tiny but intriguing teeth of N. wardi, P. distans and A. cf. cappettai are currently exposed at the GAMPS.

Paleoenvironmental Reconstruction

According to Benvenuti et al. (2014), the S3 deposits exposed at and around Certaldo are part of a delta system prograding toward the open shelf. The vertebrate assemblages from the vicinities of Certaldo corroborate the paleoenvironmental reconstruction of the Certaldo paleo-area as comprised of warm-water, more or less open shelfal settings (Collareta et al. 2020c, 2021c). Among the Certaldo quarry, barnacles are represented by abundant specimens of Concavus concavus, many of which preserve articulated opercular plates, thus suggesting a low-energy marine environment (Coletti et al. 2021).

Geosite Proposals

For centuries, the Pliocene deposits of Tuscany have been the location of prime discoveries of marine fossil vertebrates (Collareta et al. 2021a). Although many of these finds have significantly contributed to science, most historical discoveries lack precise geographic and stratigraphic whereabouts, which results in a reduction of their scientific value (e.g., Landini 1977; Cigala Fulgosi et al. 2009). Furthermore, correlations between continental and marine assemblages have always been difficult, thus compromising paleoenvironmental reconstructions. In this respect, the paleontological, geological, and sedimentological features of the three investigated quarries appear very promising.

The sediments and fossils occurring at La Serra contribute to depicting a complex paleoenvironmental landscape consisting of continental, lacustrine, and marine habitats along a Late Pliocene Tuscan coast. The vertebrate fossil assemblage concurs with the abundant record of sedimentary structures and trace fossils making this site an ideal setting for manifold geological and paleontological studies. Thus, La Serra represents an optimal scenario for providing a synoptic glimpse into the Piacenzian paralic ecosystems of Tuscany, as well as for elaborating novel correlations between terrestrial, freshwater, and marine vertebrate assemblages. The spatial closeness between the prominent historical site of Montopoli (Bartolini-Lucenti et al. 2022, and the many references therein) and the newly discovered locality of La Serra do also promise to shed new light on the chronostratigraphic and paleoenvironmental significance of the vertebrate assemblage from the former, for which precise geographic and stratigraphic whereabouts are somewhat wanting. Not least, the occurrence of an exceptionally remarkable invertebrate assemblage—including two holotypes (Garassino et al. 2012) and the geologically youngest lingulides of the Mediterranean Basin (Di Cencio et al. 2021)—further highlights the scientific value of the La Serra quarry.

The Arcille quarry represents an impressive case of a relatively limited area hosting an abundant, taxonomically rich marine vertebrate assemblage. Paleontological highlights of this quarry include the holotypes of Casatia thermophila, Nebriimimus wardi and Osteocallis leonardii, the exquisitely preserved skeletons of Metaxytherium subapenninum and aff. Makaira sp., and the highly diverse shark and ray assemblage. As regards the elasmobranchs in particular, the pioneering studies on the Tuscan Pliocene assemblages that were conducted in the late nineteenth and early twentieth centuries (e.g., Lawley 1876) suffer a lack of stratigraphic control. The stratigraphically informed sampling that is currently ongoing at Arcille provides a unique opportunity to investigate a time-constrained, paleoenvironmentally contextualized fossil fauna.

The integrative studies that are currently being conducted at Certaldo demonstrate that even abandoned extraction areas can prove relevant from scientific and conservationist viewpoints. The Certaldo area may be regarded as an optimal candidate for the establishment of a “diffuse geosite”, where paleontological data stemming from distinct but similar nearby outcrops are presented in a synthetic way at a single site, thus allowing for a comprehensive paleoenvironmental reconstruction.

Can we consider these three Tuscan quarries as potential geosites? As reported by Reynard (2008), since the end of 1990s, the assessment of geosites has followed three main groups of criteria, dealing respectively with the environmental impact (the so-called EIA procedure; see also Rivas et al. 1997; Cendrero and Panizza 1999), the land planning (Stürm 1994; Grandgirard 1999), and the promotion of the geoheritage (Panizza and Piacente 2003; Brilha 2016, 2018; Reynard et al. 2007, 2016; Gioncada et al. 2019), the latter including also geotouristic aspects. Reynard (2005) proposed a hierarchy of observations for the assessment of geosites (see also Reynard 2008; Reynard et al. 2016) that is based on the recognition of main features (e.g., the scientific attributes of the investigated site) and additional ones (e.g., its cultural and ecological qualities). Following this evaluation protocol, we found that the La Serra, Arcille, and Certaldo quarries are characterized by scientific relevance, due to the innumerable fossils (including several important specimens) and geological features that they host, but also by cultural, aesthetic, and educational attributes.

As reported by Henriques and Dos Reis (2015), a further approach to the classification of paleontological goods has been proposed by Page (2003). This scheme, which focuses on fossil specimens rather than on their locations, defines four categories of fossils based on their scientific importance. The categories proposed by Page (2003) and resumed by Henriques and Dos Reis (2015) are listed in Table 1. Based on this approach, the La Serra and Certaldo quarry features specimens belonging to categories 4, 3 and 2 (including a giant tail spine of ?Dasyatidae indet., a rare tooth of Pachyscyllium distans and the paratype of N. wardi), whereas the Arcille quarry features specimens belonging to categories 4, 3, 2 and 1 (including the holotypes of C. thermophila, N. wardi and O. leonardii).

Table 1 Classification scheme for fossil specimens from paleontological geosites.
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Baucon and Neto de Carvalho (2008) reported on a new ichnolagerstätte from the Carboniferous of the Carnic Alps (Italy and Austria), summarizing its relevance as a paleontological geosite in terms of main (crucial) and accessory (ornamental) features. Building upon Baucon and Neto de Carvalho’s (2008) approach, here we provide a synthetic overview of the geoheritage of the three investigated quarries in Table 2. All things considered, we contend that La Serra, Arcille, and Certaldo should be regarded as geosites that not only are relevant for ongoing and perspective research efforts but also comprise promising locations for dissemination and geotourism activities.

Table 2 Major features of the three studied quarries in light of a modified version of Baucon and Neto de Carvalho’s (2008) evaluation scheme
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Geoheritage Valorization and Geotourism Suggestions

Geotourism is a worldwide growing phenomenon (Dowling 2011). As reported by Newsome and Dowling (2010), geotourism promotes the conservation of geosites and the understanding of geosciences through geo-trials, guided tours, and fieldtrips. As already mentioned, the La Serra, Arcille and Certaldo quarries have all it takes to be converted into geosites for geotouristic purposes. Modern technologies can be employed for an optimal valorization of the geological and paleontological heritage of these localities (see also Pasquarè Mariotto and Bonali 2021). For instance, 3D tools (including modelling, animation, and rendering) and Augmented Reality (AR) could be put into action in multiform ways at the three quarries in order to facilitate scientific popularization and reach out to the widest public.

The following paragraphs propose specific interventions aimed at promoting and valorizing the important heritage of the three studied quarries.

La Serra Quarry

The active condition of the La Serra quarry represents a potential obstacle to the preservation of its geological and paleontological heritage. Because of the digging activities, converting the quarry into an open-air museum or equipping it with permanent installations are not available options. As regards geoconservation, a plan of continuous monitoring should be developed and put into effect in close cooperation with the quarrymen as the extractive operations advance. This will allow for monitoring of the geomorphological evolution of the quarry, characterizing the volumes of sediment that are brought to outcrop and screening the fossils that are brought to light contextually. In the last few years, abundant 2D and 3D data have been collected for monitoring purposes. Enhancing this collection of multimedia may prove useful for organizing temporary museum exhibits detailing the impact of the extraction activities on the morphology of a given area. Using drone photogrammetry (Fig. 6a, b), 3D interactive reconstructions of the quarry at different times (Fig. 6c) may be elaborated, thus providing the general public with efficient virtual time lapses depicting the modifications undergone by the quarry. It is important to remind that, although extractive activities can lead to destructing fossils, they can also contribute to exhuming and discovering others. In this respect, the abundant and diverse fossil assemblage from the La Serra quarry is exemplary. This allows for thinking of a virtual “paleo-exhibition” in which each member of the vertebrate association could be placed in its corresponding paleo-habitat. Furthermore, this quarry has been the location of our first AR tests, which consisted in projecting 3D reconstructions of some selected fossils and reconstructed animals at the corresponding finding points (Fig. 7).

Fig. 6
figure 6

Aspects of drone-based photogrammetry. a Mavic Pro drone; b Photo acquisition in the field; c 3D model of the La Serra quarry; d 3D model of the Arcille quarry; e 3D model of the Certaldo quarry. The 3D models were created with Agisoft Metashape

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Fig. 7
figure 7

Applications of Augmented Reality at the La Serra quarry. a Projection of a partly excavated proboscidean vertebra at its finding place; b Projection of a tiger shark (Galeocerdo cuvier) where a tooth belonging to this species was found. The resolution of the images is affected by the compression applied by the mobile display

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Arcille Quarry

The relevance of the paleontological features of the Arcille quarry is broadly acknowledged: protecting, promoting, and valorizing this remarkable heritage is thus necessary. At present, the Arcille quarry is quiescent. In the event that the quarrying activities do not resume, this area may prove suitable for the establishment of a geopark, thought of as both a geotouristic and an educational spotlight. The relative accessibility of the quarry makes it a promising destination for open-air lessons and field trips dedicated to school groups and academics as well as to the general public. During these activities, several tools may be provided to the audience such as flyers depicting the positioning and pictures of the most iconic sedimentary structures, and an illustrated list of the fossil assemblage yielded by the sediments cropping out at the quarry. Practical activities (e.g. fossil “hunting”) may also be proposed, especially to the youngest visitors, for exemplifying how geologists and paleontologists work in the field. To involve the visitors in the most effective way, virtual tools may also be employed, including AR. Application of AR during field trips could include the projection of interactive and animated 3D models of bones, skeletons, or even reconstructed organisms on mobile displays such as the visitors' smartphones. Informative pop-ups can also be linked to these objects. Drone-based 3D models of the quarry could also be used to provide a bird's eye view of the fossiliferous area (Fig. 6d). Keeping in mind that the Arcille quarry is privately owned, depending on the owner’s availability, permanent installations such as explanatory panels about the regional geology and the history of paleontological discoveries can be placed along the outcrops. Furthermore, real-size reconstructions of selected representatives of the fossil assemblage may also be put into action.

Certaldo Quarry

The Certaldo quarry has been dismissed for a long time, which allowed vegetation to grow uncontrolled and mud to accumulate at the foot of the quarrying surface. Keeping in mind that the safety of visitors is of crucial importance for geosites (Dowling 2011), the first steps of our restoration program should involve securing the quarry area. After wild bush removal, paths have to be traced to establish a field itinerary. Consequently, the whole area would be transformed into a free-entry geosite where different informative installations may take their place. Thus, the Certaldo quarry may serve as the core of a “diffuse geopark”, where paleontological data stemming from distinct but similar nearby outcrops would be presented in a synthetic way at a single site. The walls of the quarry may provide a sort of natural stage where all the species discovered at the various outcrops around Certaldo could join together in the same virtual environment, including e.g. the killer whale-like dolphin Hemisyntrachelus sp. from Canonica, the pelagic eagle ray Aetobatus cf. cappettai from the vineyard locality, and the catshark Pachyscyllium distans from the quarry itself. In this framework, the application of AR may prove extremely useful by allowing the projection of virtual reconstructions of all these faunal elements. Furthermore, drone-based photogrammetric reconstructions of the other Certaldo outcrops and their fossils could be built and shown as a virtual background of the exhibition (Fig. 6e). Thanks to AR, the visitors may be able to visualize all the 3D reconstructions on their mobile devices, which in turn would allow for several kinds of interaction, including learning more about the featured organisms just by clicking on their displays. Field trips organized at the Certaldo quarry would thus become thoroughly interactive, involving the visitors at 360 degrees and exemplifying the enormous potential of 3D digital technologies in Earth Sciences. To make the visitors experience an even more realistic trial of the Tuscan Pliocene sea, the animal reconstructions could be implemented by means of animations and “reality-inspired” swimming movement patterns. Such a virtual geosite proposal has the potential to envision a comprehensive requalification plan for an abandoned, yet scientifically relevant, quarrying area.

Fossils and Museums

Conservation of the geological heritage is often intended as limited to site-based approaches (Henriques and Dos Reis 2015) thus excluding the displaced elements of that heritage, such as geological and paleontological samples that are stored in museums (Prosser et al. 2011). That said, fossils do in fact comprise a moveable heritage, and the issues of conservation do not stop when specimens are collected, thus becoming part of the “ex-situ” heritage (Page 2003). As regards the three Pliocene quarries investigated herein, many relevant vertebrate fossils have been placed in Tuscan museums and research facilities, being (or in the process of becoming) part of permanent exhibitions (Fig. 8). In particular, the holotype of Casatia thermophila is part of the “cetacean gallery” of the MSNUP, being placed besides skeletons of its closest living relatives (the white whale and narwhal), thus highlighting its importance for reconstructing the evolutionary origins of these iconic high-latitude cetaceans (Fig. 8a). At the same museum, the most complete billfish specimen from Arcille (a partly prepared skeleton) is also exposed in a room devoted to the “behind the scenes” of vertebrate paleontology (including the excavation, preparation and restoration phases). Several shark and ray specimens from all the investigated localities (including the giant stingray stinger from La Serra, Carcharhinus limbatus and the paratype of Nebriimimus wardi from Arcille, and Pachyscyllium distans and Aetobatus cf. cappettai from Certaldo) are exposed at the GAMPS, where they contribute significantly to depicting the impressive elasmobranch diversity of the Pliocene Tyrrhenian Sea. The Metaxytherium subapenninum skeletons from Arcille and some tetrapod specimens from La Serra (including postcrania of terrestrial mammals) are part of the “Pliocene room” of the GAMPS, which is devoted to illustrating the impressive paleoenvironmental and taxonomic diversity reflected by the Tuscan Pliocene fossils and fossil localities (Fig. 8c). Some significant remains from La Serra, Arcille and Certaldo have recently been moved to a new, adjacent exhibition room at the GAMPS—one that is devoted to the dissemination of the most recent and scientifically relevant paleontological discoveries from Tuscany.

Fig. 8
figure 8

Examples of musealization. a Museo di Storia Naturale dell’Università di Pisa: exhibit of the holotype of the cetacean Casatia thermophila from the Arcille quarry besides its extant relative Monodon monoceros; b, c Museo Geopaleontologico Scienze della Terra GAMPS: exhibit of a diverse collection of shark teeth from Tuscany, including specimens from the investigated quarries (b), and skeletons of the sirenian Metaxytherium subapenninum from the Arcille quarry (c)

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Fossils and Fossil Hunting

The initiatives proposed herein have the aim of promoting the geopaleontological heritage of these important geosites in the near future. In order to make this program possible, a crucial issue has to be dealt with, namely, the illegal collection of fossil materials. In this respect, the Italian legislation (law n. 1089 of 1939 and “Codice dei Beni Culturali e del Paesaggio” of 2004) clearly states that all the fossils occurring on Italian land belong to the Italian state, such that their collection, private storing, and trade are by no means allowed. Fossils found throughout the Italian territory must be available for study, storage, and exhibit. Although illegal fossil collection is widespread in Italy, some examples of virtuous collaboration between quarrymen, museums, amateur paleontologists, and academic researchers do also exist. Such partnerships represent good examples of “citizen science” (Bonney et al. 2016) that may also work well in the elaboration and implementation of efforts of scientific dissemination as well as to make the local communities aware of the enormous relevance of the Tuscan paleontological heritage.

Conclusions

Quarries represent privileged locations for geological research, teaching, and dissemination. Many quarries have long been home to innumerable fossil finds. Tuscany hosts lots of active, inactive, and abandoned quarries from which amazing vertebrate fossils have been collected. Here, we studied three Tuscan quarries where Pliocene sediments are extracted. All these sites are relevant as regards their geological and paleontological heritage, being home to diverse sedimentary structures as well as to remarkable vertebrate fossil assemblages that support their recognition as geosites. Valorization proposals, including temporary exhibitions, open-air activities, and virtual tours, were suggested for all three sites, which are representative of active, inactive, and abandoned quarries, respectively. 3D technologies (i.e., virtual reconstructions, animations, augmented reality, and drone-based photogrammetry) are identified as a likely useful tool to approach people outside the academia. Musealized specimens are not always assessed when evaluating the importance of geosites, even if fossils are a major constituent part of geoheritage. These “ex-situ” paleontological goods and their exhibit in dedicated museums represent an important and irreplaceable tool for promoting awareness of geosites and geoheritage.