Micromorphological features of soils formed on calcium carbonate–rich slope deposits in the Polish Carpathians

Seven soil profiles developed on calcium carbonate–rich slope deposits in the Polish Carpathians were studied in order to: i) determine the micromorphological features of heterogeneous soils formed in a carbonate depositional environment, and ii) track primary and secondary calcium carbonate forms and their distribution in such stratified soils. Three cases of soils with different arrangements of calcium carbonate were distinguished, controlled mostly by slope processes. For instance, the increasing content and random distribution of angular and subangular rock fragments found in the overall soil matrix and the irregular coarse: fine size limit suggested different intensities of accumulation and mixing of soil material transported along the slope. Slope processes, together with the calcium carbonate content, mineralogical characteristics and texture influenced the type and arrangement of the bfabric pattern. The calcium carbonate distribution within the soils, besides the obvious inheritance from parent material, was governed by the translocation and mixing of deposits on slopes. The climatic conditions prevailing in the area favour the development of secondary forms of calcium carbonate. However, only three of the seven studied profiles contained pedogenic forms of calcium carbonate, yet they were distributed randomly. The occurrence, distribution and preservation of secondary carbonates depended on the content of primary calcium carbonate and soil features such as texture. The transported material down the slope may indicate a very low content of primary calcium or lack thereof, hence its pedogenic forms could not be created.


Introduction
Soils located on slopes often exhibit a high level of heterogeneity and stratification within the solum. The formation of such soils is usually driven by geomorphological activity, mostly slope processes of various durations and intensities (Alijani and Sarmandian 2014;Badía et al. 2013;Kacprzak and Derkowski 2007;Kowalska et al. 2017;Waroszewski et al. 2013Waroszewski et al. , 2015. Often, the development of mountain soils is also supported by admixture of allochthonous materials, which is an additional cause of their heterogeneous character (Jäger et al. 2015;Philips and Lorz 2008;Waroszewski et al. 2015Waroszewski et al. , 2018. The heterogeneity of soils developed from slope deposits can be seen in macroscopic observations of morphological features such as sudden changes within the grain size distribution (Kowalska et al. 2017;Waroszewski et al. 2013Waroszewski et al. , 2015, the presence of rock fragments with different lithology, a significant change of Micromorphological features of soils formed on calcium carbonate-rich slope deposits in the Polish Carpathians percentage content and/or shape of coarse fragments (Kacprzak and Derkowski 2007;Kowalska et al. 2019), various degrees of soil weathering, and changes in the colour mantle or the soil conciseness (Schaetzl and Anderson 2005). However, transported, displaced and mixed material on slopes can be also efficiently recognized by a number of micromorphological features. Sometimes, even in the absence of macroscopic indications, the analyses of micromorphological features can give even more detailed insight (Bertran and Texier 1999;Mücher et al. 2010).
Unfortunately, micromorphological features in soils affected by slope processes have not received much attention in recent years. Reviewing the literature, the most complex investigations were published nearly forty years ago and were associated with micromorphological aspects mainly concerning solifluction deposits (e.g. Harris 1981; Harris and Ellis 1980;Mücher et al. 2010 and references cited in each) and colluvial deposits (e.g. Govers et al. 1994;Mücher and Morozova 1983;Mücher et al. 1981;van Oost et al. 2000;van Muijsen et al. 2002). The 1990s abounded in fairly well documented micromorphological studies concerning slope deposits (see Mücher et al. 2010 and references therein). According to these authors, translocated or displaced material may be recognized by the presence of horizontally oriented rock fragments, rounded or subrounded rock fragments and/or subangular aggregates composed of material derived from other soil horizons, as well as certain pedofeatures, e.g. ferruginous nodules, often with sharp boundaries, and variously distributed clay secondary forms with disorientated character. However, the intensity and duration of slope processes can deeply alter original microstructures within the slope deposits in terms of the character, size and the abundance of micromorphological features.
Many scientists have shown an interest in the calcium carbonate features visible in thin sections in various kinds of soils (Durand et al. 2010;Sehgal and Stoops 1972;Wieder and Yaalon 1974). One of the most comprehensive overviews has been given by Reeves (1970), dealing mainly with diagenetic carbonate features and their classification and origin. Some authors have focused on a general description of calcium carbonate microfeatures in terms of their shape, properties and morphology (e.g. Bullock et al. 1985). Further studies have investigated the mechanism of formation and development of secondary calcium carbonate features, which are precipitated and very often subjected to recrystallization (Durand et al. 2007(Durand et al. , 2010Zamianian et al. 2016) and dissolution processes (Alonso et al. 2004;Zamanian et al. 2016).
However, the occurrence and distribution of calcium carbonate microfeatures in mountain soils can be more complex than other areas, because of the activity of slope processes that control their translocation as well as their various distribution within the solum (Alijani and Sarmandian 2014;Bockheim and Douglass 2006;Gargiulo et al. 2013). To date, there have also been a few studies that have given attention to calcium carbonate microfeatures within slope deposits, but these studies have a rather local character. Zasoński (1992Zasoński ( , 1993Zasoński ( , 1995a has defined a set of characteristic micromorphological features of calcium carbonate soils on slopes within the Carpathian Foothills and Eastern Carpathians (South Poland). Afterwards, Zagórski (1999) studied the micromorphological features of carbonate soils developed under very variable geological conditions with a strong influence of ancient and contemporary deluvial processes, in the area of the Pieniny Mts. (Polish Carpathians). More recently, Kacprzak and Żyła (2006) supported the thesis that microstructures and pedofeatures observed in micromorphological analyses can confirm the occurrence of lithic discontinuities between slope cover and bedrock in carbonate-rich Cambisols. On the other hand, Kolesár and Čurlik (2015) investigated autogenous carbonate accumulations in loess soils, using Trnavská pahorkatina loess hilly land (SW Slovakia) as their case study.
Nevertheless, none of the abovementioned studies focused on both the influence of slope processes on micromorphological features in soils developed from slope deposits and assessments of the occurrence and distribution of lithological and pedogenic forms of calcium carbonate in such heterogeneous soils. Therefore, the aim of this study was to give a more detailed insight into the above-stated problems by assessing the micromorphological picture of mountain slope soils.

1 Study area and sampling procedure
The study focused on seven soil profiles located within the Polish part of the Carpathian Mts. (Figure 1), where Jurassic and Cretaceous sedimentary formation prevailed and which mainly present calcium carbonate-rich rocks, e.g. limestone and marl, as parent material. Carpathian flysch sediments occur as well, e.g. sandstones, shales and conglomerates, also indicating the carbonate character of the region (Skiba 1995).
The soil cover of the Carpathian Mts. is a function of lithology, relief and vegetation. A few types of soils may be distinguished. Generally, the occurrence of limestone and marl as well as other calcium carbonate-rich rocks (e.g. sandstone, shale) provides parent material for Leptosols, Eutric Cambisols and Regosols (60%). In some parts, Dystic Cambisols occur (30%), which developed on more acidic rocks (mostly alluvial material). Further, a small part of the Carpathian Mts. soil cover (10%) consists of Stagnosols, Gleysols as well as Regosols, formed on siliceous and non-carbonate substrates (Kowalska et al. 2017(Kowalska et al. , 2019Skiba 1995).
The mean annual air temperature for the western Carpathians Mts. ranges between 6°C and 8°C at 700 m a.s.l. and 4°C-6°C at 1100 m a.s.l. At the highest elevations, the mean air temperature ranges between 2°C and 4°C (Otrębska-Starklowa et al. 1995). Mean annual precipitation varies between 400 and 700 mm. The sum of evaporation can reach up to 300-400 mm in the period from May to October. The duration of snow cover is about 120 days per year on the highest peaks (Otrębska-Starklowa et al. 1995).
The soils under study show seven different examples of calcareous parent material as well as various patterns of calcium carbonate distribution within the profile (Figure 2). The soils have developed from various carbonate-rich colluvial materials (Table 1) and represent different reference soil groups according to the World Reference Base for Soil Resources (IUSS Working Group 2015; Table 1). Meteorological data (the sum of precipitation, evaporation and the temperature) given by Kuźniar et al. (2011) and the collection of the Polish Institute of Meteorology and Water Management for the period 1990-2005, from selected meteorological stations located near the studied soils (Limanowa, Krościenko nad Dunajcem, Rabka, and Niedzica) were used for this study.
Soil samples were collected from all designated soil horizons (39 genetic horizons in total) for further micromorphological and physicochemical analyses. Soils were sampled under normal humidity conditions (moist). Characteristics of their morphology were identified, and a detailed description of the soil profiles constructed in accordance with the requirements of FAO (2006). The O horizons were not taken into account during the morphological and micromorphological description of the soil profiles. The soil samples were air-dried and sieved through   a certified plastic sieve (2 mm diameter). For all soil samples, besides the micromorphological analysis, the following analyses were performed: total organic carbon (TOC), total nitrogen (TN) and calcium carbonate (CaCO 3 ) content, soil texture, pH, as well as total potential acidity and base saturation. The colour of each separate horizon was determined using the Standard Soil Colour Charts (Munsell 1975).

Physical and chemical analyses
The soil texture was determined using the Bouyoucos aerometric method according to the Polish standard PN-R-04032 (1998). Potentiometric measurements of pH were taken using a standard combination electrode and a CPI-551 Elmetron pH meter in 1 M KCl solution at a ratio of 1:2.5 and H 2 O. TOC content was determined by applying the Tiurin method, using potassium dichromate and Mohr's salt without the removal of calcium carbonate. TN content was determined using the Kjeldahl method (Lityński et al. 1976) on a FOSS Kjeltec TM 8100 apparatus. Total CaCO 3 content was determined by the Scheibler method using hydrochloric acid (Lityński et al. 1976). The evaluation of base saturation was calculated from the total potential acidity (TPA), which was assessed via incubation of soil samples in 0.5 M of calcium acetate at pH 8.2, and the sum of exchangeable bases (Ca 2+, Mg 2+, Na + and K + ), assessed via extraction in 1 M ammonium acetate at pH 7.0 (Kociałkowski et al. 1984) and analysis with an ICP-OES Optima 7300 DV.

Micromorphological soil characteristics
In order to provide a comprehensive analysis of the micromorphological features in the studied soils, thin sections from undisturbed soil material were prepared with a 'Kubiena box'. Sampled soil material with undisturbed structure was consolidated in an Epovac vacuum chamber and impregnated using either an epoxy resin (Araldite ® 2020) for profile P1, or a polyester resin (POLIMAL ® 109) for profiles P2, P3, P4, P5, P6, P7. Thin sections were prepared by a set of special equipment, including an Epovac vacuum chamber (Struers ® ), a CS30 saw for soil sample cutting (Struers ® ), a CL50 apparatus for precision lapping of thin sections (Logitech ® ) as well as a CL50 apparatus for thin-section polishing (Logitech ® ). Microscopic observation of thin sections was conducted using a Nikon Eclipse 400 microscope, using both plane-and cross-polarized light. Each thin section was described in accordance with the nomenclature proposed by Stoops (2003).

Results
Based on morphological features and primary and secondary calcium carbonate content and their distribution ( Table 2, Table 4), the soils under study were classified into three main groups indicating different calcium carbonate arrangements within the soil profiles. However, all soils had calcium carbonate-rich C horizons. The groups were as follows: (1) lithogenic (and in some horizons also pedogenic) calcium carbonate was present in all horizons; (2) lowermost B and C horizons showed primary calcium carbonate; (3) slight or strong content of primary calcium carbonates present only in the C horizons.

Morphological characteristics, chemical properties and texture
The presence of primary calcium carbonate in all soil horizons was characterized in three soil profiles, -P1, P2 and P3 -classified as Calcisol, Cambisol and Regosol, respectively (Table 1, Figure  2). However, in the field any secondary forms of calcium carbonate were recognized; the pedogenic calcium carbonate was visible only in the thin sections. The number of coarse fragments in these soils was highest in the BC and/or C horizons and generally increased with depth. The shape of coarse fragments was mostly angular (P2 and P3) or angular/subangular (P1) ( Table 2).
J. Mt. Sci. (2020) 17 (6):  topsoil. The lowermost horizons also showed a variable texture in each profile. Within P1, the lowermost horizons had loam and silt loam textures (Table 3). The silt fraction prevailed in the lowermost horizons of P2, where clay loam, loam and silty clay loam textures were noted. Similarly, a silt fraction prevailed in P3. The lowest horizons of P3 had clay loam and silt loam particle size classes (Table 3). Each profile of Group 1 was characterized by pH values increasing with depth ( Table 4). The pH values varied vertically within the profiles from weakly acidic to neutral, ranging from 7.8 to 8.8 in H 2 O and from 6.5 to 7.6 in KCl solution (Table 4). CaCO 3 was present in every soil horizon, usually at a very high content (up to 703 g·kg -1 in the middle part of P1, Table 4).
carbonate occurred only at depths from 60 to 110 cm in the form of geodic ( Figure 4f) and typic ( Figure 4d) CaCO 3 nodules. The presence of secondary carbonate accumulation in P3 was visible at depths from 20 to 90 cm forming a dense microsparitic matrix (Figure 5d; Table 5).
Within the whole of the P1, P2 and P3 profiles, the iron-manganese impregnations were seen (e.g. Figure 4a, c, e; Figure 5e). Additionally, rounded, diffused, iron-manganese orthic nodules were noted within the Ahk1 and 2Ck1 horizons of P1 and upper horizons of P3. In terms of other pedofeatures, fragments of infillings of illuvial clay and typic clay coatings were noted in P2 ( Figure 4b) and P3 (Figure 5f) in the middle and lower parts of the soil profiles, respectively (Table 5).
Organ and tissue residues as well as fragments of organic fine material were present down to 40 cm in P1. Within P2, organ ( Figure 4e) and tissue residue occurred in whole profile. The soil P3 was characterized by the occurrence of organ residues in every horizon and tissue residues in A horizons (Table 5).
Within P1 and P2, limestone was visible, sometimes with calcite veins (Figure 3b). In the surface horizon of P3, the fragments of shale occurred. Moreover, quartz, plagioclase and clay minerals were also seen in the studied profiles (Table 5).

Morphological characteristics, chemical properties and texture
Profiles P4 and P5 were examples of primary calcium carbonates enriching the middle and lower part of soil profiles (Table 1, Figure 2). Both profiles were classified as Stagnosols (Table 1). Soils P4 and P5 were characterized by the occurrence of the mosaic of colours typical for stagnic properties. In some places, the presence of black manganese concentrations and iron mottles  was identified. The coarse fragment concentrations ranged from 5 to 30% (P4) and from 15 to 60% (P5) and generally increased downward soil profile (Table 2).
Considering the grain size distribution of P4, the silt fraction predominated in every horizon, reaching values higher than 50% (fine silt and coarse silt in total, Table 3), allowing the classification of the fraction group as silty loam to depths down to 70 cm and as silty clay loam below 70 cm. The highest silt fraction was noted in the Ap and ABw horizons, where the silt content ranged between 55 and 69%. In the lowest horizons (3BCtg1 and 3BCtg2), the clay fraction increased at the expense of the silt fraction (Table 3). Similarly, the silt content was also the highest in P5, especially in the upper horizons; for example in AB, the fine silt and coarse silt in total was 64%. Below 15 cm, the content of clay fraction increased, allowing classification as silty clay loam (Table 3).
Calcium carbonate in P4 occurred at depths from 18 cm to more than 90 cm and ranged from 2.20 to 37.5 g·kg -1 . Calcium carbonate in P5 occurred from 30 cm to 90 cm, indicating a more homogenous pattern, ranging from 31.2 to 34.9 g·kg -1 . The P5 soil had a higher percentage content of base saturation, compared to profile P4. However, pH values were very similar in both profiles and ranged from 6.1 to 8.4 in H 2 O and from 5.1 to 7.6 in a KCl solution (Table 4).

Micromorphological soil characteristics
In soils P4 and P5, the subangular blocky ( Figure 7e) and vughy microstructure as well as planar ( Figure 7e) and vughs (Figure 7a, c) type of voids were recognized in almost every horizon (Table 5). In the Ap and ABw horizons of soil P4 and the AB horizon of P5, the crumb microstructure and compound-packing and channel void types were identified (Figure 6a). The related distribution pattern, the porphyric type, was seen, with different fine and coarse ratios in both profiles (Table 5A; Figure  7b, d, f) types of b-fabric dominated at depths from 0 to 60 cm; below 60 cm only the speckled type of b-fabric was recognized (Table 5A).
No secondary carbonates were recognized in P4 and P5. However, many clay secondary forms such as infillings of illuvial clay and typic clay coatings were seen (Table 5; Figure 6f; Figure 7d). Within the pedofeatures, iron-manganese impregnations were noted in every horizon ( Figure  6c; Figure 7b, f), together with rounded, diffused, iron-manganese orthic nodules in the upper (P4) and middle (P5) parts of soil profile.
Organ and tissue residues occurred in almost all upper and middle horizons of P4 and P5. In terms of rock fragments, sandstone and shale (Figure 6c, d) were present in every horizon (Table  5). Focusing on the mineral arrangement, quartz was present within the whole solum (e.g. Figure  6b); however, plagioclase was indicated in the   horizon only at depths down to 48 cm (Table 5). In soils P4 and P5, primary carbonate minerals were found only within the middle and lower horizons.

Explanations
down the soil profile (Table 2). However, the soil profiles demonstrated different contents of coarse fragments: within soil P6, coarse fragments ranged from 5% to 90% and within soil P7, merely from 5% to 10% (Table 2). With respect to the size grain distribution of P6, the total quantity of sand (~60%) dominated in A horizons; this sandy loam texture of the topsoil allowed the foreign nature of this horizon to be diagnosed. In lower horizons, the content of sand decreased, accompanied by an increasing silt and clay fraction, which reached up to 50% and 30%, respectively. The content of fine and coarse silt and clay varied. At depths of 8 to 46 cm, a silty loam texture was seen; below this, in sequence silty clay loam, clay loam and loam were identified. Such an arrangement suggests stratification within the profile (Table 3). Soil P7 showed a different pattern in terms of texture. At depths down to 22 cm, in the horizons Ah and Bt the clay fraction prevailed (31%-39%, Table 3) giving them a clay loam texture. Below, the increase of the silt fraction was noticeable. Often the silt fraction reached more than 50%, and silt clay loam and silt loam were seen (Table 3). The size grain distribution suggested a high heterogeneity of P7.
The calcium carbonate levels in P6 and P7 soils were 9.83 and 113 g·kg -1 in the 3C and 2BCtg horizons, respectively (Table 4). Nonetheless, soil P7 was characterized by higher pH values and a higher base saturation compared to profile P6 (Table 4). A very high variability of TOC was noted within the whole profile of P6. The TOC values in P6 did not indicate any clear trend and ranged from 8.80 to 39.6 g·kg -1 (Table 4). Atypically, the highest values of TOC were in horizon 3C, which might evidence a level of high mixing of the soil material (Table 4).

Micromorphological soil characteristics
The A horizon of P6 showed a granular microstructure with compound packing and channel voids. The horizon 2AB represented a  vughy microstructure with vughs types of voids. All horizons lying below these showed a subangular blocky microstructure and a planar void type (Figure 8a, c, e). Profile P7 was homogenous in terms of microstructure and voids (Table 5); only subangular blocky and vughy microstructure together with planar and vughs types of voids were recognized (Figure 9a, e). Similar to the other studied soils, P6 and P7 indicated a porphyric type of related distribution pattern, with various size limits of c:f (Figure 9a, c). Besides, the partially undifferentiated type of b-fabric in A horizon of P6. Usually, mainly porostriated (Figure 8b; Figure 9f) and partially speckled (Figure 8b; Figure 9b) types of b-fabric were noted in soils P6 and P7.
Within P6 and P7, no secondary calcium carbonate was found. Moreover, clay pedofeatures were seen mostly in the form of fragments of infillings of illuvial clay as well as typic and crescent types of clay coatings (Figure 8b, d, f; Figure 9b, d, f), which were unevenly distributed within the solum. The rounded, diffused, ironmanganese orthic nodules were recognized some horizons, and however more often the ironmanganese impregnations were identified ( Figure  9e).
Within soil P6 mostly organ and tissue residues were visible in the upper part of the soil profile. Organic fine material occurred within the whole profile of P7, with plant organ and tissue residues rarely seen, only in the Ah horizon. Only quartz and fragments of sandstone were recognized within soil P7 (Table 5). In profile P6, plagioclase and clay minerals and fragments of menilite shales (Figure 8c, d) were also seen.  The soil material had been relocated on slopes to various degrees and intensity, which was evident in the current occurrence and arrangement of micromorphological forms, e.g. the various distribution of coarse fragments, subangular and angular shape and elongated position of coarse fragments, the changes of c:f size limit in soil matrix and sudden changes of b-fabric within the solum (Tables 2 and 5A). Moreover, the presence of fragments of pedofeatures evidenced activity of slope processes (see Section 4.2). Such a heterogenic character and organization of soil microfeatures within soils located on slopes have been often noted in various studies, e.g. Bertran and Texier (1999); Bertran et al. (1997); Harris (1998); Kacprzak and Żyła (2006); Kehl et al. (2018); Mücher et al. (2010); Müller and Thiemeyer (2014); and Waroszewski et al. (2013).
For instance, the signs of soil mass transport and mixing along the slope were represented by the shape and distribution of coarse fragments within the horizons ( Table 2). The studied soils indicated three different types of influence by slope processes on the coarse fragment distribution. On the one hand, the abrupt increase and random arrangement of coarse fragments was often seen between the upper/upper and middle and lower horizons, as in profiles P2, P3, P4, P5 and P6 (Table 2), where a large change, e.g. from 25% in 2Bt horizon up to 90% in 2Ck2 horizon in case of P2, was noted. In the case of profile P1, the content of coarse fragments undoubtedly increased, but after all, represented a high content of coarse fragments within the whole profile (from 30% -Ahk1, to 85% -3C3; Table 2). P7 was an example of a different kind of distribution of coarse fragments, and presented a homogenous but rather low content of rock fragments (from 5% -Bt and Btg, to 10% -2Btg2 and 2BCtg; Table 2), suggesting that the fine-grained soil material was probably washed out during transport on the slope (Kowalska et al. 2019;Mücher et al. 2010).
Further, the orientation of coarse fragments was evidence of the great impact of the slope processes on the studied soils. An elongated position of rock fragments was noted on some profiles (e.g. profile P2, Figure 4a, b; profile P3, Figure 5a, b), indicating that the material had been subject to gravity-driven processes (Kacprzak et al. 2015;Kowalska et al. 2017;Mücher et al. 2010;Watson and Watson 1967). Moreover, the coarse fragments mostly had an angular shape (in some samples also subangular, e.g. P1, P4, P5 and P6; Table 2) and random orientation, which could be interpreted as a result of short-distance transport (Dill 1998;Jäger et al. 2015;Waroszewski et al., 2013). Yet the morphology of coarse fragments seen in this study differed from the results of other authors, e.g. Bertran and Texier (1998); Harris (1998);Mücher et al. (2010); and Müller and Thiemeyer (2014), who noted mostly (sub) rounded rock fragments in heterogeneous colluvial soils. However, the common, angular shape of rock fragments in the soils under study could be conditioned by weak intensity or duration of transport on the slope and/or the small distance between the initial spot of displaced material and the site where it ultimately accumulated (Kleber 1997;Kowalska et al. 2019;Lorz et al. 2010).
Together with the shape of coarse fragments and the groundmass character, the coarse and fine size limit (c:f ratio) should be highlighted in terms of assessment of the impact of slope processes on the studied soils' formation. The c:f-related distribution pattern in the studied soils included mostly porphyric (open porphyric, double spaced porphyric, single-spaced porphyric, close porphyric) with various ratios of fine and coarse fragments (Table 5). Based on the determined c:f ratio, it can be assumed that the mixing of materials affected the studied soils differently. Profiles P1, P2 and P3 represented abrupt changes within the coarse and fine size limits at the boundary, where the lithic discontinuity was seen. This may suggest that upper horizons above the lithic discontinuity may have the same origin, which caused the similar arrangement of coarse and fine fragments in those horizons, or the process of mixing overlap extensively contributed to homogenizing of this part of the soil profile (Waroszewski et al. 2018). Following this assumption, in the other soils (P4, P5, P6 and P7) where a higher variability in c:f ratio was noted, the degree of mixing process was slightly weaker. Another explanation for such different patterns in the c:f ratio may be the different times and intensity of deposition and accumulation processes of soil material (Stoops and Jongerius 1975;Mücher et al. 1981).
The large influence of slope processes led to heterogeneity in fine-grained material distribution as well. The alternation between the content of the fine and very fine sand and silt fractions was noticeable (Table 3), giving rise to the three main patterns in fine-grain size distribution in the studied soils and showing the various effects of slope processes. In the soils P1 and P6, the surface horizons had a strictly fine-sandy character (horizons Ahk1 and Ahk2 -soil P1, horizon A -soil P6; Table 3), however, a sudden decrease in the content of fine and very fine sand in favour of silt was stated. Such patterns could not be exclusively the result of sandstone weathering, therefore most likely these surface horizons were deposited as a result of soil material transport down the slope (Waroszewski et al. 2013). Furthermore, profiles P2, P3, P4 and P5 were characterized by a silty character in both the surface and lower horizons. Nonetheless, the content of fine and very fine sand gradually decreased, suggesting at least two reasons for this decrease: i) the allochthonous, aeolian input of fine fractions within the whole profile and/ or ii) gradual accumulation of soil material through e.g. grain-flow deposits (Mücher et al. 2010 and literature cited therein). On the other hand, in soil P7, the distribution of the finegrained fraction was quite varied, hence a high degree of mixing could be supposed in this case (Waroszewski et al. 2018).
The studied soils indicated an irregular arrangement of b-fabric patterns (Table 5), which may be derived from both the soil chemical features, such as calcium carbonate content distribution and mineralogical characteristics and texture, as well as undoubtedly soil material transport on the slope and its intensity. The presence of a partially crystallitic b-fabric in soils P1, P2 and P3 may be connected with the high content of randomly distributed small crystals of calcite (or other minerals like quartz) and the occurrence of recrystallized, secondary forms of calcium carbonate (Figure 3d, f; Figure 4d, f; Figure 5d; Table 5). Often, porostriated, granostriated and speckled b-fabric patterns were noted due to oriented clay domains around voids or aggregates (Bullock et al. 1985), as in case of P2, P3, P4, P5, P6, and P7 (Figure 5b Table 5). Rarely, the partially undifferentiated b-fabric pattern was visible on studied thin sections, suggesting masking of the interference colour in the micromass (Stoops 2003). Usually, the soils showed a very heterogeneous arrangement of bfabric patterns among the soil profile as well as their coexistence in one horizon, which most likely resulted from transport and deposition of the soil material prior to reworking by mass movement on the slope (Gerasimova and Lebedeva-Verba 2010;Harris 1998;Kovda and Mermut 2010;Mücher et al. 2010).
Iron-manganese impregnations (Table 5; Figure 4a (Table 5) recognized in studied thin sections were usually characterized by gradual (diffuse) boundaries. According to the literature, orthic nodules and iron-manganese impregnations are generally formed in situ and not moved (Stoops et al. 2010). As noted by Lindbo et al. (2010) and the literature cited therein, rounded orthic nodules and ironmanganese impregnations have been considered as a reflection of current soil hydrology, especially short periods of water and moderate rainfall; this is consistent with the water conditions of the studied soils (Table 1). However, McCarthy et al. (1998) consider the rounded shape of impregnations and nodules as evidence of being transported not formation in situ. Considering the fact that studied soils are supposed to be under strong soil material translocation processes on these slopes, the assumption of McCarthy et al. (1998) seems reasonable.

The relations between layering of slope deposits and calcium carbonate distribution in soils
The translocation and mixing processes of the soil material on the slopes highly influenced the distribution of primary and secondary calcium carbonate within the studied soil profiles. Similar findings have been seen by other authors studying carbonate soils, e.g. Badía et al. 2013;Kacprzak and Salamon 2013;Kowalska et al. 2019. In this study, primary (lithogenic) calcium carbonate occurred mostly due to the presence and weathering of calcium carbonate coarse fragments, e.g. limestone, sandstone and shale, throughout the profile (Tables 1 and 2, Figure 2). Contrarily, secondary (pedogenic) carbonate formation was an outcome of the pedogenic process, i.e. dissolution and precipitation (Ferńandez-Ugalde et al. 2010;Zamanian et al. 2016). The process of evapotranspiration could ensure secondary carbonate movement (upward) and diffusion (unidirectional) (Ferńandez-Ugalde et al. 2010;Zamanian et al. 2016).
Primary calcium carbonate enrichment was detected in all soil horizons of P1, P2 and P3 (Table  4; Figure 2). Nonetheless, within the profiles P4, P5, P6 and P7, a sudden reduction of calcium carbonate content was noted, mostly in the A, AB and/or B horizons (Table 4). This seems to be the result of leaching of calcium carbonate in less stable soil conditions, causing a neutral or slightly acidic reaction of the soil (Gunal and Ransom 2006;Rubio and Escudero 2005;Scheatzl and Anderson 2005). However, in the case of heterogeneous soils located on slopes, the loss of carbonates from soil by leaching (decarbonation) is sometimes doubtful (Alijani and Sarmadian 2014;Badía et al. 2013). Thus, different causes leading to carbonate removal should be emphasized. First, erosion and deposition of the non-carbonate material on the surface of in-situ soil might be one reason for the patterns of calcium carbonate distribution seen (Kacprzak and Derkowski 2007;Reheis et al. 1992). On the other hand, the primary calcium carbonate could be removed from the soil substrate upon the start of mass wasting processes, and then postsedimentary processes (pedogenesis) can be launched (Ciolkosz et al. 1979;Kleber 1997).
While the reasons for primary calcium carbonate distribution within soil seem to be fairly obvious, the presence and arrangement of secondary carbonates is more complex. According to thin-section observations, the pedogenic carbonates were visible only in soils of Group 1 -P1, P2 and P3 (see Section 3.3). It has been widely reported in the literature that one of the significant factors controlling the pedogenic carbonate formation and localization are climate conditions, i.e. temperature and the sum of precipitation and evaporation (Egli and Fitze 2001;Hough et al. 2014;Landi et al. 2003;Zamanian et al. 2016). As was noted by other authors (e.g. Birkeland 1999;Zamanian et al. 2016) pedogenic carbonates can be formed during the process of soil drying, when the evapotranspiration exceeds the precipitation. Although, arid and semiarid climates seem to be ideal for pedogenic carbonate formation, due to the long evaporation-dominant stage, which favours the concentration stage over the dissolving stage occurring during precipitation periods (Borchardt and Lienkaemper 1999), often the presence of secondary carbonates are also noted in colder regions such as temperate climates. The climatic conditions prevailing in the studied area completely allow the formation of secondary carbonate forms (Table 1). Especially, the precipitation regime is the most important agent here, which controls the depth where pedogenic carbonates can be leached and accumulated (Candy and Black 2009;Egli and Fitze 2001;Kuznetsova and Khoklova 2012). It is accepted that the accumulation of secondary carbonates requires a at least a mean amount of precipitation about 500 mm per year (Gocke and Kuzyakov 2011;Zamanian et al. 2016).
On the other hand, it is suggested that increasing dryness and evaporation increases the rate of carbonate precipitation (Candy and Black 2009). Gocke and Kuzyakov (2011) noted that the temperature is the key factor; the lowest rates of carbonate accumulation are supposed to occur at 10°C and the highest at 30°C. Following this assumption, the mean average annual temperature at the studied area is below 10°C (Table 1), which suggests that the intensity of carbonate precipitation was rather low. Furthermore, such low intensity together with relatively moderate rainfall could contribute to the development of secondary carbonates of small size that usually become more irregular with broken faces ( However, taking into account comparable climatic conditions in all studied soil profiles the question arises why the pedogenic carbonates were able to develop only in soils P1, P2 and P3? It is supposed that the first reason is the very high content of primary calcium carbonate and generally very stable conditions in these soils: high pH, high base saturation, moderate moisture, etc., which do not allow secondary carbonate dissolution (Zamanian et al. 2016).
Nonetheless, a different distribution of secondary calcium carbonates was recognized in Group 1. Within soil P1, pedogenic carbonates enriched the soil profile down to depths of 65 cm (Table 5). This soil was characterized by loam texture, with the clear addition of sand in its upper part. Such a character of the soil mantle (sanddominated) provides conditions for the easy leaching of carbonates (Durand et al. 2010;Wieder and Yaalon 1974). This prompts the question of why would calcium carbonates then remain in the soil? We can only speculate that the slope cover from which soil P1 developed was deposited quite recently and the secondary calcium carbonates have just formed (Durand et al. 2010;Zamanian et al. 2016). This hypothesis is supported by the occurrence of dispersed very small-sized secondary calcium carbonate forms, e.g. nodules (about 1 mm, Figure 3d, f), and by soft forms like impregnations, which may be evidence of being in a very early stage of development (Gile 1993;Kovda et al. 2003;Zamanian et al. 2016). Furthermore, the loose material might also provide the conditions for easy movement of pedogenic calcium carbonate within the soil profile; this is why in the relatively young sediments the secondary forms were present in almost the entire soil column (e.g. profile P1).
A different case is shown in the profiles P2 and P3. No clear trend can be established, as the content of primary calcium carbonate was rather various between the soil horizons (Table 4, Figure  2). Within those soils, the pedogenic calcium carbonates were present in the lower parts of the soil profile (Table 5). This may be because the fact that soil material from the upper part, being under a slope process, could have been partially decalcified; the content of calcium carbonate was noticeably lower at depths of 60 and 20 cm and below in P2 and P3, respectively, compared to the lower-lying horizons. On the other hand, the secondary calcium carbonate preservation in lower-lying horizons (horizons: 2BkC and 2Ck1 in soil P2 and 2BCk, 2BCkt1 and 2BCkt2 in soil P3) may be related to the texture. The horizons in which pedogenic carbonates were seen had a loam and clay loam texture, which tends to prevent pedogenic carbonate movement (Wieder and Yaalon 1982).
Due to the arrangement of lithogenic calcium carbonate in P4, P5, P6 and P7 (Group 2 and 3) and the absence of its pedogenic forms, it is not certain if the soils were enriched in calcium carbonate or whether its carbonation was caused by slope processes. Even if the soils had a high content of calcium carbonate in the entire profile at the beginning of their formation, slope processes (e.g. soil washing, mixing) could lead to depletion or loss of calcium carbonate from the soil material (Alijani and Sarmadian 2014). As the result, the calcium carbonate was preserved in horizons that were not under strong redeposition processes (Kowalska et al. 2019). In such unstable environments, where even primary calcium carbonate forms are barely preserved, development of secondary carbonates was most likely not possible. Similar findings were noted in soils developed on loess-like sediments, where complete remodelling of carbonate loess might lead to a disappearance of primary carbonate in the soil profile (Li et al. 2017;Pye 1987;Waroszewski et al. 2018;Zasoński 1983).

Conclusions
The heterogeneous character of the studied soils was seen in the occurrence and distribution of several micromorphological features. Mostly, increasing content and random arrangement of angular and subangular coarse fragments were noted between the upper, middle and lower parts of the profiles, suggesting re-depositional processes. The slope processes led to stratification, as evidenced in the soil profile through e.g. various c:f ratios. On the one hand, the strongest differences in c:f ratio were noted at the boundary of the lithic discontinuity. On the other, it is likely that a similar origin or the advanced mixing of soil material led to homogenization and resulted in less different c:f ratios within the profile. The presence and irregular distribution of various types of bfabric (e.g. crystallitic, porostriated, granostriated and speckled) were very likely due to a derivative of both the soil features, such as secondary calcium carbonate content, mineralogical characteristics and texture, as well as soil material transport on the slope.
The climate conditions (temperature, precipitation, evaporation) prevailing in the area favour the development of secondary forms of calcium carbonate. However, only three of the seven profiles had pedogenic forms of calcium carbonate, distributed randomly. Occurrence, distribution and preservation of secondary carbonates mainly depend on a high content of primary calcium carbonate and soil features such as texture. On the other hand, the material transported down the slope might indicate a lack of or a very low content of primary calcium, hence its pedogenic forms could not be created. The slope processes may lead to depletion or loss of calcium carbonate from soil material. In such unstable conditions, where even primary calcium carbonate was barely preserved, the formation of secondary carbonates was most likely not possible.