Introduction

During the Serravallian, significant paleoenvironmental changes occurred in the Central Paratethys (CP) Sea, as evidenced by studies from Kováč (2000), Piller et al. (2007, 2022), Hohenegger et al. (2014), Ruman et al. (2017), Nováková et al. (2020), and Kranner et al. (2021a, b). The northeast corner of the Vienna Basin (VB) has been extensively studied through local paleontological research at sandpits and road cuts, as documented by Mišík (1974), Švagrovský (1981), Baráth et al. (1994), Sabol and Holec (2002), Hyžný et al. (2012), Bitner et al. (2014), Pivko et al. (2017), Ruman et al. (2017), and Šujan (2019). However, a comprehensive study synthesizing these findings is lacking. The red algal genus Lithothamnion significantly influenced the local lithofacies, forming reefs, carpets, and bioherms of upper Badenian (Schaleková 1969, 1973). These limestones are younger than the well-studied Leitha Formation limestones (Kysela 1988; Schmid et al. 2001; Mišík and Reháková 2009; Wiedl et al. 2013, 2014; Harzhauser et al. 2020). The discussed limestones, sometimes referred to as the St. Margarethen (Harzhauser et al. 2020); and Rákos limestones (Császár 1997), correlate with the NN6 lower part and Bulimina–Bolivina Zone (younger than 13.53 Ma), as indicated by Hudáčková et al. (2003), Jamrich and Halásová (2010). This study aims to reassess archival and new upper Badenian sections to understand the eco-space genesis and the variability between clastic and carbonate facies in the Slovak part of VB. It also examines shallow water formations, using their genesis as a key distinguishing factor. In addition, the study seeks to map these limestone occurrences throughout the CP and elucidate the mechanisms of their origin.

Geology

The deposits below the studied interval consist of the Jakubov/Baden formations, extending from the inner to outer shelf, and from the carbonate Leitha Formation. These formations, older than 13.8 Ma (Vass 2002; Fordinál et al. 2013; Harzhauser et al. 2020), are situated below the Langhian/Serravallian boundary in the Central Paratethys (CP). The 13.8 Ma numeric boundary date is supported, e.g., by Lukács et al. (2015) in Hungary and Šarinová et al. (2021) in Slovakia. This study primarily focuses on the late Badenian strata, characterized by the muddy Studienka/Rabensburg formations, dated younger than 13.8 Ma. These formations comprise a variety of environments from the outer shelf to inner shelf and lagoons, as noted by Špička (1966), Vass (2002), Kováč et al. (2008a), Harzhauser et al. (2020), and Piller et al. (2022). The Sandberg Member of the Studienka Formation, representing marginal inner shelf facies, consists of conglomerates and sandstones intercalated with algal limestone beds (Baráth et al. 1994). Notable limestone types include algal-biodetritic limestone, as found in the Kúty-45 well (Kováč et al. 2008b). This environment, initially sandy coastal plains, evolved with rising sea levels, promoting the growth of Lithothamnion reefs. The age of these deposits is determined through analyses of mollusk, foraminifera, nannofossil assemblages, and 87Sr/86Sr dating (Hudáčková et al. 2003; Hyžný et al. 2012; Fordinál et al. 2014; Harzhauser et al. 2020; Harzhauser 2022a, b, c). The overlying Sarmatian-age Holíč Formation, encompassing muddy and sandy layers, changes from outer shelf to deltaic settings (Vass 2002; Kováč et al. 2008a; Hudáčková et al. 2021). The basin margin features the Karlova Ves Member in Slovakia and its Austrian equivalent, the Wolfsthal Member, comprise sandy-coquina and oolitic limestones, transitioning into upper cross-bedded sands (Nagy et al. 1993; Vass 2002; Harzhauser and Piller 2004; Harzhauser 2022a, b, c). Thus, the environment, interpreted as bryozoa-serpulid reefs (Harzhauser and Piller 2004; Piller and Harzhauser 2023) was later submerged by fluvial ecosystems.

Methods

The shallow-water sedimentary structures and paleoenvironment were identified based on Rossi et al. (2017) and Pellegrini et al. (2020). Field facies analysis followed standard procedures (Boggs 2006; Nichols 2009). Thin sections were prepared from samples ranging from algal limestones to sandstones and examined under a polarizing microscope. They were utilized for sedimentary microstructure description and foraminifera identification.

Samples were picked from various sedimentary environments (Figs. 1, 2). From Zelené terasy (ZT) construction site 17 samples, Devínska Nová Ves–Bratislava automobile works–BAZ (BAZ) 2, Stupava–Vrchná hora (VH) 5, Jabloňové (J) 11, Kuchyňa (K) 1 and Rohožník–Vajarská (RV) 2 samples were collected for biostratigraphy and paleoecology analyses. All essential layers were measured, labeled, and photo documented.

Fig. 1
figure 1

a Miocene Chrono/lithostratigraphic framework of the Vienna Basin and the location map of the studied sections. Timescale adapted from Krijgsman and Piller (2012); the lithostratigraphic details follow Špička (1966), Baráth et al. (1994), Vass (2002), Kováč et al. (2004, 2007, 2008a, b), Fordinál et al. (2013), Harzhauser et al. (2019, 2020, 2022), Csibri et al. (2022); global sequences after Haq et al. (1988) and Hardenbol et al. (1998), Coe (2003); CPN Zonation from Cicha et al. (1975); FAD—O. suturalis from Wade et al. (2011), FO G. druryi after Hudáčková et al. (2013), Šarinová et al. (2021). b Location of the Pannonian Basin System within Europe. c, d Position of the Vienna Basin within the Alpine–Carpathian–Pannonian region

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Fig. 2
figure 2

Lithological columns of the discussed sections (studied and archived). Note, for previously published results, see references within the figure

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Calcareous nannofossils were studied in samples from ZT5, 8–12, 15, 17; BAZ1; VH1, 5; J4, 7–9; K1; and R1, 2. Preparation and analysis follow the method of Bown and Young in Bown (1998). Further adjustments were made using methods described in Nováková et al. (2020). Counts were transposed in percentages to show the composition of the assemblages. Systematic identification and taxonomy follow Young (1998) and Young et al. (2017). Standard NN zones are after Martini (1971) and Hilgen et al. (2012). Paleoenvironmental characteristics follow the concept of Ćorić and Hohenegger (2008) and Auer et al. (2014).

Foraminiferas were examined from ZT1–17; BAZ1–2; VH1–5; J1–10; K1. Samples were prepared sensu Ruman et al. (2017). Taphonomic analysis was applied using the methods of Holcová (1999). Foraminiferas were measured using a micrograph scale. Systematic identification and taxonomy follow Cicha et al. (1998) and Hayward et al. (2023).

Palynological analysis was performed on samples from ZT4–12 and 14–17. Processing utilized standard methods described in Doláková et al. (2021). Microscopy and imaging were performed using a Zeiss Axioskop 40 (400–630 × magnification), Axiocam ERc 5 s camera, and SEM microscope QUANTA FEG250.

Newly obtained data (foraminifera and calcareous nannoplankton) to evaluate the eco-space variability were combined with datasets from published results from Rohožník Konopiská (RK) shallow wells V-42, V-44 (Čierna 1973; Fuksi 2015), Záhorská Bystrica landfill (ZB), and Stupava clay pit (SC) shallow wells (Šujan et al. 1992; Hudáčková and Kováč 1993), Devínska Nová Ves clay pit (D) (Kováčová and Hudáčková 2009; Jamrich and Halásová 2010), Devínska Kobyla Hill localities (DK, L, FL, G, DSi, S) (Hyžný et al. 2012), Stupava–Vrchná hora (VH) (Hrabovský 2013; Hrabovský and Fordinál 2013), Devínska Kobyla Medieval quarry (MQ) (Pivko et al. 2017), and Devín–Záhrady construction site (DZ) (Ruman et al. 2017) (Fig. 2).

The statistical coupling analysis was applied based on the established taxonomical concept for calcareous nannoplankton (Jamrich and Halásová 2010). Due to the limitation of various approaches to foraminifera species determination in different publications (Čierna 1973; Kováčová and Hudáčková 2009), some species were grouped based on similar ecological preferences. Species of the Bulimina genus were grouped to Bulimina ex gr. elongata, species of the Bolivina genus were grouped according to their morphology into 1) flat smooth and 2) inflated cancellate groups, species of the genus Elphidium were split into 1) keeled and 2) non-keeled elphidia (sensu Haynes 1981; Murray 2006). Diversity indices (SSD- simple species number diversity), Shannon_H, Simpson, and Fisher α were used (Hammer et al. 2001).

Statistical methods, such as non-metric multidimensional scaling (NMDS), cluster analysis, and principal component analysis (PCA) (Bray Curtis similarity—BC) were applied on benthic foraminifera (with foraminiferal number ≥ 70) and calcareous nannoplankton, and processed by Paleontological Statistics, ver. 4. 03 (PAST) (Hammer et al. 2001) and POLPAL software (Walanus and Nalepka 1999) for distribution charts. Data were exported (Supplements 1, 2) from Microsoft Excel, Microsoft Access database adjusted by Hudáčková and Hudáček (2001).

87Sr/86Sr dating

The value of the 87Sr/86Sr ratio from Eocene to present, characterized by a steep marine Sr isotope curve, can be calibrated to the numerical time scale with an accuracy of up to 500,000 years, although in the period between 15 and 13 Ma, the change in 87Sr/86Sr ratio slowed down significantly; thus, numerical dating is also much more imprecise. Freshwater input affects the normal marine 87Sr/86Sr ratio, which causes a problem. The period of normal saline waters in the CP lasted from the Oligocene to the end of the Badenian (~ 12.7 Ma), so the SIS for dating these formations could be applied (Less 2020). 87Sr/86Sr results of Fordinál et al. (2014) and Less (2020) are referenced within this paper.

Results

Sedimentary facies

ZT—description

The Zelené Terasy (ZT) composite profile is situated on the eastern end of Devín district (48°10′35.47′′ N, 16°59′48.29′′ E). The profile comprises four sections, designated I to IV (Figs. 2, 3). These sections were formerly a part of a construction pit. Section I, located at the southern end of the profile, starts with an ochre-colored, massive, fossiliferous sandy mudstone (Sfm; refere to Figs. 2 and 3 for facies codes). Sfm sharply and angularly contacts a massive, fossiliferous, bioturbated brown-gray mudstone (Fm; Fig. 3). Fm facies extends into section II, where it is in an erosive contact with a matrix-supported, poorly sorted, and poorly rounded conglomerate that contains clasts ranging in size from granules to boulders. This facies is around 130 cm thick and extends to the top of the section. The matrix is sandy, with abundant bioclasts. Limestone and sandstone are present both in detrital and clast form (Gm; Fig. 3). The algal-biodetritic limestones represent redeposits and can be described as white patches with ochre coating and sandy mudstone matrix. Clasts of these limestones can reach from few centimeters up to several meters in diameter (Fig. 3). Section III comprises a 40 cm thick gray massive mudstone (Fm; Fig. 3) overlain by a thin (1–2 cm) red layer containing iron oxides. A 40 cm thick, mauve-colored massive, fossiliferous sandy mudstone follows (Sfm; Fig. 3). Above, a brown-gray massive, fossiliferous mudstone (Fm) occurs again. Section IV is located at the northernmost end of the profile and begins with a 30 cm thick gray mudstone (Fm). In the middle part of the section, a 10 cm thick, indistinctly laminated sandy mudstone appears (Fig. 3; Sfl).

Fig. 3
figure 3

© 2022, yellow circle and line show the location and orientation of the profile on the map; b section with facies description and details; the white lines represent the internal structure and boundaries of a scour fill and other lithofacies intervals. Paleobathymetries are implied from the interconnection of the study by Pellegrini et al. (2020) with Rossi et al. (2017), Boggs (2006), and Nichols (2009). Nevertheless, please note that the paleobathymetries are only orientational; c 1—Parvamussium cristatellum, 2a,b—Varicorbula gibba, 3—Thracia convexa, 4—Turritella sp., 5—Karnekampia lilli, 6—Paroxystele orientalis, 7—Glossus humanus, 8—Tasadia carniolica

ZT studied profile. a Location map adopted from Google Earth Pro, Image

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J—description

The Jabloňové section (J) is situated in an abandoned sandpit south of the Jabloňové village (48°20′26.67′′ N, 17°6′6.49′′ E). The section (Fig. 4) commences with a 70 cm thick massive, fossiliferous, bioturbated, medium- to fine-grained sand facies well-sorted and rounded, with few plant fragments (Sm; refer to Fig. 5 for facies codes). Above this facies is a 20 cm thick graded, fossiliferous, bioturbated, matrix-supported gravel with granule to pebble-sized well-sorted and rounded clasts (Gg). An alternation of Sm and Sfm facies characterizes the remaining 220 cm of the section. Sfm facies comprise massive, fossiliferous, bioturbated muddy sands with a few plant fragments.

Fig. 4
figure 4

© 2022; b–h section with facies descriptions and specific details; d, e Venerid bivalve. For explanatory notes on lithofacies, see Fig. 5

Jabloňové sandpit studied profile. a Location map adopted from Google Earth Pro, Image

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Fig. 5
figure 5

Jabloňové sandpit: lithofacies description and interpretation

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BAZ—description

The BAZ section (Fig. 6) is north of the Devínska Nová Ves–Bratislava automobile works (BAZ) (48°14′36.75′′ N, 16°58′22.09′′ E). The facies comprise massive, bioturbated, fossiliferous sandy mudstones with bivalve rock cores and Lithothamnion clasts (Sfm). These facies extend deeper into the substratum, spanning more than 70 cm in thickness. The section then continues with a weathered layer (~ 30 cm thick), followed by a soil layer at the top (~ 30 cm thick).

Fig. 6
figure 6

© 2022; b, d, e, f detailed sections with facies descriptions/interpretations and specific details of Lithothamnion and bioclasts; c articulated bivalve casts

BAZ (Bratislava automobile works) studied section. a Location map adopted from Google Earth Pro, Image

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Nannoplankton

Eight samples of the ZT section (Fig. 2) were studied (ZT5, 8–12, 15, 17). Thirty-four Neogene taxa were determined, abundance and preservation are moderate. The most abundant samples, 11, 5, 10, 8, were dominated by small and medium-sized reticulofenestrids (Fig. 7, Supplement 1) up to 68.45% in sample 10 (Reticulofenestra haqii 28.88–68.45%). Apart from autochthonous, rare reworked Lower Miocene, Paleogene, Cretaceous taxa were observed represented by Helicosphaera ampliaperta, Reticulofenestra lockeri, Helicosphaera compacta, Micula staurophora, Prediscosphaera cretacea, Cribrosphaerella ehrenbergii. Simpson diversity ranges from 0.3975 to 0.801, with the highest in sample 9. Stratigraphically important taxa include Orthorhabdus rugosus (ZT9–12, 17) and Braarudosphaera bigelowii parvula, Helicosphaera wallichii, R. sicca, Sphenolithus abies.

Fig. 7
figure 7

Calcareous nannofossils. a, b Rhabdosphaera sicca, ZT5, ZT17; c Syracosphaera pulchra, ZT5; d Sphenolithus abies, ZT8; e, f Helicosphaera wallichii, ZT5, ZT11; g Helicosphaera carteri, J4; h Braarudosphaera bigelowii parvula, ZT10; i Triquetrorhabdulus milowii, ZT8; j–l Orthorhabdus rugosus, ZT9, ZT11, J9; m Umbilicosphaera jafari, BAZ1; n Umbilicosphaera rotula, ZT9; o Holodiscolithus macroporus, ZT9; p Pontosphaera multipora, ZT5; r Reticulofenestra haqii, ZT5; s, t Reticulofenestra pseudoumbilicus, ZT8, J4; u Coccolithus pelagicus, ZT9

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Cluster analysis of percentages by Ward’s method (Fig. 8a) split ZT samples into three clusters (distance level 27, Supplement 3a), and similar three clusters were distinguished on distance level 60 within entire new data matrix (Fig. 8b, Supplement 3b). NMDS analysis (Fig. 9) based on Bray Curtis similarity and proved stress by Sheppard diagram 0.1054 grouped studied assemblages into three groups: group 1 – ZT samples with the prevalence of R. haqii, group 2 – J4, 7, 8 and K1 samples C. pelagicus, group 3 – BAZ1, J9, R1, R2 and VH5 samples with high equitability (Supplement 1).

Fig. 8
figure 8

Cluster analysis (Ward’s method from percentages). a Zelené terasy (ZT) solely; b all newly studied sites including ZT (Supplement 3a, b). Explanatory notes: 1, 2, 3 = individual clusters, and locality symbols apply for all figures

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Fig. 9
figure 9

Non-metric multidimensional scaling (NMDS) analysis (Bray Curtis from percentages). For explanatory notes, see Fig. 8

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NMDS percentages correlation of nearby localities (Fig. 10a) with Sheppard diagram stress 0.1244 shows three groups. Reticulofenestrids dominated Group 1 (mainly composed of D and ZT). Group 2 (S, J, K samples) with C. pelagicus and R. pseudoumbilicus, and Group 3 (BAZ1, R, VH5) with the prevalence of R. minuta. Samples J9 and VH1 (not shown) are considered outliers. PCA (Fig. 10b) of ZT and all sites used for correlation distinguish three main groups. G1 with mainly D, ZT10, S1.1 samples discriminated by R. haqii, G2 dominated by S, ZT, J, K with C. pelagicus, and G3 with D, ZT, J, BAZ1, VH, R with R. minuta.

Fig. 10
figure 10

a NMDS (Bray Curtis from percentages) analysis of the nannofossil association; b principal component analysis (PCA) biplot analysis of all localities with dominant taxa expressed by green lines (including published results from DNV clay pit and Sandberg; Jamrich and Halásová 2010; Hyžný et al. 2012). For explanatory notes, see Fig. 8

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New calcareous nannoplankton data were combined, analyzed, correlated, and evaluated with datasets from published results. The listing of additional results is in alphabetical order:

Devínska Nová Ves–Bratislava automobile works (BAZ)—new data (Figs. 2, 6). The exceptionally rich nanno sample consists mainly of R. minuta (46.51%) and C. pelagicus (27.2%). Stratigraphic important taxa are Pontosphaera japonica, R. sicca, R. pseudoumbilicus, Calcidiscus premacintyrei, S. abies, Coronocyclus nitescens (elliptical) (Supplement 1).

Jabloňové sandpit (J)—new data (Figs. 2, 4). Four samples (4, 7–9) were analyzed for nannofossils dominated by C. pelagicus (J7 59.15%) and stratigraphic important taxa, including H. wallichii, Orthorhabdus serratus, O. rugosus, R. pseudoumbilicus, S. abies, Triquetrorhabdulus milowii (Supplement 1).

Kuchyňa (K)—new data. One sample studied for nannofossils, and foraminifera includes mainly C. pelagicus (47.61%), R. pseudoumbilicus (9.52%), H. walbersdorfensis (Supplement 1).

Rohožník (R)—new data were obtained from two samples of Lithothamnion limestone from Vajarská. R1 has impoverished diversity dominated by R. minuta (30.76%). R2 includes mainly R. minuta (12.5%) T. milowii (12.5%) with no index fossils (Supplement 1). Only poor nannoflora was mentioned in Hladilová et al. (1998).

Stupava–Vrchná hora (VH)—new data. Two nannofossil and five samples of foraminifera were analyzed. From VH1 C. floridanus, Reticulofenestra sp., T. carinatus were identified. Sample VH5 from Lithothamnion limestone consists only of long-ranging species R. minuta (43.47%), C. pelagicus (8.69%), U. jafari (8.69%) with no index fossil or zonal marker (Supplement 1).

Devínska Kobyla Hill (DK) and Sandberg (S) (Hyžný et al. 2012; Pivko et al. 2017; Ruman et al. 2017). However, 48 samples were analyzed by Hyžný et al. (2012), we used 11 of these samples (S1.1–1.4, S1, S2.1–2.6; Supplement 1). The main nannofossil assemblage composition represents C. pelagicus, C. floridanus, R. haqii, R. minuta, R. pseudoumbilicus, and other age-supporting taxa Calcidiscus macintyrei, C. premacintyrei, C. tropicus, H. carteri, H. wallichii, S. abies, U. jafari.

Devínska Nová Ves tehelňa–DNV clay pit (D)—The calcareous nannoplankton list was adopted from Jamrich and Halásová (2010), with 69 samples analyzed. The main taxa are C. pelagicus, R. haqii, R. minuta, R. pseudoumbilicus, B. b. parvula, H. wallichii, H. macroporus, R. sicca, S. abies, S. pulchra.

Foraminifera

Seventeen samples (1–17) of benthic foraminifera from the ZT section were studied in detail. In total, 86 Neogene taxa were determined (Fig. 11). Preservation of foraminiferal tests is good to moderate. Bulimina species are most abundant in the entire profile (up to 90% in 4–7 and 17), followed by Bolivina (ca. 30% in 5–6), Cassidulina (up to 30–35% in 15, 12, 8, 5) and keeled elphidia (ca. 30% in 13, 3 and 1). Individuals of Melonis were well represented (up to 20%) in 16, 14, 10, 9, 2. Dimensions (width/length) of benthic foraminifera (770) with mass prevalence of elongated forms from samples 4, 5, and 6 were measured to reveal a possible taphonomic effect (Fig. 12, Supplements 2, 3c).

Fig. 11
figure 11

Foraminifera. a Globigerinella obesa, BAZ; b Dentoglobigerina altispira, BAZ; c D. altispira wall detail, focused on the crust covered with the nannofossils, yellow arrows show coccoliths, BAZ; d Elphidium josephinum, ZT; e Bulimina elongata, ZT; f Bulimina subulata, ZT; g Bolivina maxima, ZT; h Uvigerina semiornata, ZT; i Trifarina bradyi, ZT; j Pappina parkeri, ZT; k Melonis pompilioides, ZT; l Nonion commune, ZT; m Porosononion granosum, ZT; n Porosononion granosum, VH; o Ammonia inflata umbilical side, J; p Ammonia inflata spiral side, J; q Lobatula lobatula umbilical view, VH; r Lobatula lobatula apertural view, ZT; s Biasterigerina planorbis umbilical view, K; t Biasterigerina planorbis spiral view, K; u Textularia gramen, ZT; v Textularia pala apertural view, J; w Rosalina obtusa umbilical view, BAZ; x R. obtusa wall detail, focused on crust of the nannoplankton coccolith, yellow arrows show coccoliths, BAZ; y R. obtusa wall detail, focused on crust with coccolith, BAZ; z Borelis melo, VH

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Fig. 12
figure 12

Boxplots illustrating benthic foraminifera width/length ratio with mass dominance of elongated forms (ZT4, 5, 6), documents wide size shell variability without size sorting (Supplement 3c)

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Cluster analysis based on the Bray Curtis similarity index shows three groups (A, C, D) and outlier (B) at the ca. 68 similarity level (Fig. 13a, Supplement 3d), similarly as shown by PCA and NMDS analyses (Figs. 13b, c).

Fig. 13
figure 13

Statistical analyses of the foraminifera association (ZT locality). a Cluster analysis (Ward`s method from percentages) shows three groups A dominated by Ammonia/Elphidium genera, C dominated by Bulimina/Bolivina, D grouped highly diversified samples (Supplement 3d); b Shows same groups resulted from PCA biplot with dominant taxa expressed by green lines; c NMDS (Bray Curtis from percentages) with oxygen content as a main discriminant

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From BAZ, two foraminifera samples were studied. BAZ1 from washed residue over 1 mm contains a lot of Amphistegina tests, Bryozoa, red algae, and crab claws. Most foraminifera tests are coated by coccolith-rich crusts (Fig. 11) and comprise 90% of the fine (0.071–1 mm) residue. The assemblage (SSD 22) contains common Lobatula lobatula (32%), Cibicides sp. div. (10%), Biasterigerina planorbis (17%) together with Textularia pala, Cancris auricula, Elphidium fichtelianum, Reussella spinulosa, and Sphaerogypsina globulus, rare infauna was badly preserved. Plankton includes Globigerina bulloides, G. regularis, and Dentoglobigerina altispira. Sample BAZ2 contained many mollusk shells, echinoderm fragments, Cirripedia, and fish bones. Foraminifers (SSD 20) are similar to BAZ1, the most abundant is L. lobatula (33%), with the umbilical part strongly affected by the shape of the substrate. The rare planktonic group contains mainly G. bulloides and D. altispira specimens. Small specimens of Globocassidulina, Hansenisca, and Nonion with different shell preservation are also present.

Eight samples from the J and K unveiled new data, two were barren. Sample J4 in fine-grained residuum contains a foraminifera-rich assemblage (SSD 21) dominated by Ammonia inflata, small non-keeled elphidiids as Elphidium excavatum and P. granosum, accompanied by rests of echinoids, shark teeth, and mollusks shell debris. The dominance of A. inflata (to 35%) is stable within the entire profile (Supplement 2). Species diversity values are from 8 (J10) to 24 (J4). K yields associations rich in L. lobatula, Cibicides sp., T. pala, and elphidiids (SSD 22).

Foraminifers from VH profiles are generally in coarser-grained residue, containing sharp-edged quartz and large mica crystals. Foraminiferal tests are poorly preserved, often with clasts stacked into the foraminiferal test complicating the determination of specimens. Foraminifers are scarce in samples 3, 4 were more abundant and consisted of well-preserved specimens dominated by B. planorbis, E. crispum, E. rugosum, A. inflata, Guttulina austriaca, Globulina striata (Supplement 2). Sample 5 is solid algal limestone, and foraminifers were studied in thin sections. Abundant Borelis melo, Quinqueloculina, Triloculina, Amphistegina sp. were identified.

NMDS analysis of the data matrix using Bray Curtis similarity (Fig. 14a) shows four distinct groups: the first group with low SSD dominated by epiphytic Biasterigerina, Neoconorbina, Ammonia; a second group with higher SSD dominated by epiphytes (Lobatula, Amphistegina, keeled elphidia), the third group of high diversified assemblages rich in Melonis, Cassidulina, flat Bolivina and Uvigerina and the fourth group dominated by Bu. elongata. Sheppard’s diagram proves stress 0.1242, confirming the NMDS result’s plausibility (Fig. 14b).

Fig. 14
figure 14

A NMDS (Bray Curtis similarity) of the newly obtained foraminifera associations; b Sheppard’s diagram of the foraminifera associations. For explanatory notes, see Fig. 8

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The new foraminiferal data of the late Badenian age were combined, analyzed, correlated, and evaluated with datasets from published results. The listing of additional results is in alphabetical order:

DK and S (Hyžný et al. 2012; Pivko et al. 2017; Ruman et al. 2017). In all studied samples from these localities, specimens of keeled elphidia are most abundant (exceeding 50%). The dominant species are E. crispum followed by Neoconorbina terquemi. The average species diversity of the studied assemblages is low (SSD 8–9). The Shannon_H and Fisher α diversity indices also reach very low values (H = 0.5–2; Fα = 0.6–6.0). The algal limestones or algal patches parts thin sections study show the prevalence of Elphidium, Miniacina, Neoconorbina/Asterigerinata, B. melo, and less porcellaneous forms such as Quinqueloculina. The most abundant coralline algal genus is Mesophyllum. Lithothamnion, Lithophyllum, and Spongites are less frequent, while thin encrustations of Titanoderma and Hydrolithon are rare (Pivko et al. 2017). In the algal limestones from Merice locality (Hyžný et al. 2012; near Lingula bed), miliolid forms (Quinqueloculina sp. div., Cycloforina contorta, Triloculina cf. tricarinata, Pseudotriloculina) prevail.

D—The foraminifera list was adopted from Kováčová and Hudáčková (2009). The profile alternates between associations dominated by plankton or benthos; only in a few samples is an association rich in both components documented. Benthic foraminifera are dominated by Pappina neudorfensis, Bolivina dilatata, Bulimina elongata. Planktonic foraminifera consist of various forms of G. bulloides and Turborotalita quinqueloba. Diversity (DSS) varies from very low (2–4) to high (72–89) (Kováčová and Hudáčková 2009).

Rohožník (R) Konopiská—Foraminifera from pelitic sediments determined Badenian and Sarmatian age. Foraminifera lists (boreholes RV-42, RV-44, Čierna 1973), Hladilová et al. (1998) and Fuksi (2012, 2015) were used. The foraminiferal assemblage was also studied in Ruman and Hlavatá Hudáčková (2015), where it was described as rich in Lobatula, Tretomphalus, Biasterigerina, keeled elphidia, small miliolid taxa Pseudotriloculina, Quinqueloculina, and Miliolina. Planktonic foraminifers are rare, represented by Globigerina.

Rohožník (R) Vajarská locality in the old limestone quarry shows a rich algal assemblage (Schaleková 1973); we studied foraminifera from new thin sections from the outcrop. The two associations were recorded—one with a dominance of L. lobatula, P. mediterranensis, Elphidium sp., Amphistegina sp., and a second with B. melo and Pseudotriloculina, Quinqueloculina, Miliolina.

Stupava tehelňa (clay pit)—Boreholes 100–150 m deep were drilled to analyze municipal waste disposal conditions. The site was assigned to the Bulimina–Bolivina Zone. The foraminiferal association is very similar to the DNV clay pit upper part, dominated by P. neudorfensis, B. dilatata, Bu. elongata in the benthic association. Planktonic foraminifera consist of various forms of G. bulloides together with T. quinqueloba and G. obesa. For our study, we adopted the foraminifera list from the report by Šujan et al. (1992) and Hudáčková and Kováč (1993).

NMDS statistical analysis of all samples (Fig. 15a, Supplement 2) shows almost the same four groups of samples as in the ZT profile together with all newly studied samples. The first is represented in the D outcrop dominated by Bulimina and Bolivina, partly in R and ZT localities with a high portion of Bu. elongata. The second group is composed of highly diversified samples R, ZT, L, G sites with the main portion of Melonis, Cassidulina, Globocassidulina, Uvigerina, the third group contains J, K, S, R, BAZ, VH, and F sites (SSD 5–20) with the prevalence of Lobatula, Amphistegina, keeled elphidia, Ammonia (Supplement 2). Sheppard’s diagram proves stress 0.197, which represents good plausibility (Fig. 15b). Principal component analysis (Fig. 16) shows five components explaining ca. 75% of variability representing original variables (the most significant species) influenced deployment of associations. The highest negative PC1 (variation in the data) component score represents flat smooth Bolivina (– 0.738), and PC2 with Uvigerina sp. div. (– 0.3414), Bu. ex. gr. elongata (– 0.2663), while the highest positive eigenvalues reach keeled elphidia (0.432) and Biasterigerina (0.169).

Fig. 15
figure 15

a NMDS (Bray Curtis similarity) of the foraminifera associations entire dataset (new and published data); b Sheppard’s diagram of the foraminifera associations. For explanatory notes, see Fig. 8

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Fig. 16
figure 16

PCA biplot analysis of the foraminifera associations entire dataset (new and published data) with dominant taxa expressed by green lines. For explanatory notes, see Fig. 8

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Palynology

Thirteen samples (Fig. 17) from ZT (4–12 and 14–17) were processed for pollen and palynofacies analysis. Samples 4, 6, 7 represent the most diversified pollen assemblage. Sample 5 has remarkably well-preserved palynomorphs but differs in palynofacies type–dominancy of Pinaceae (Supplement 4).

Fig. 17
figure 17

Palynospectra of ZT6 sample. a, b Pinus sp.; c Achomosphaera sp.; d Cathaya sp.; e Tsuga sp.

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Interpretations

Sedimentary facies

ZT: A high concentration of thick-shelled bivalves, such as Glossus humanus, and increased bioturbation levels (Sfl/Sfm and Fm) suggest a medium to high-energy environment dominated by tide and/or wave action in the shoreface to inner shelf zone (Fig. 3). This environment was affected by an incision (scour fill) caused by matrix-supported conglomerates (Gm) with poorly sorted angular clasts. This indicates gravity transport by debris flows, which could have been triggered during a sea-level fall. The emerged area is likely associated with a coastal plain.

J: Well-sorted sands (Sm, Sfm) and conglomerates (Gg) in Figs. 4h and 5 indicate wave activity from the shoreface to the inner shelf. The observed high-intensity bioturbation aligns with Rossi et al. (2017), suggesting such patterns often reflect shallow marine conditions influenced by waves. Their findings, which emphasize well-rounded sediment grains and few coal fragments, match our observations in the Gg facies (Fig. 4h). The marine bivalves venerids and hiatellids, prevalent in all studied beds (Sm, Sfm, Gg), hint at a shallow marine environment. These bivalves are typically found in high-energy, shallow waters, as stated by Stanley (1970) and Pratt and Campbell (1956). While the erosional surface at the Gg facies base does not solely denote a coastal environment, its association with the normally graded conglomerate (Gg) suggests wave-induced dynamics. Rossi et al. (2017) confirm that such graded bedding, especially with marine fauna, often results from wave action, pointing to a coastal environment.

BAZ: The abundance of well-rounded Lithothamnion and other marine bioclasts embedded in the sandy mudstones (Sfm) indicates the presence of the shelf zone (Fig. 6).

Biostratigraphy and paleoecology (nannoplankton, foraminifera)

Biostratigraphy depends on nannoplankton and foraminifera. The nannoplankton zone was assigned to the presence of O. rugosus in this study (ZT9–12, 17, J9), whose first occurrence (FO) is generally considered as at the base of NN6 (Young 1998; Young et al. 2017). Other age-supporting taxa in the studied material include B. b. parvula, H. wallichii, R. sicca, S. abies, U. jafari, U. rotula. The studied assemblage is, therefore, assigned to NN6 Zone (Martini 1971). Higher numbers of H. macroporus, mainly from ZT and K samples, as previously mentioned from the D site, support the late Badenian age (Jamrich and Halásová 2010). Foraminiferal CPN9 Zone (Central Paratethys Neogene Zonation; Cicha et al. 1975) is given based on the occurrence of P. neudorfensis and B. maxima (ZT, D, BAZ, J, R). Rich plankton assemblage dominated by Globigerina sp. div. is present only in the D, S, R, JV samples. Rare Orbulina universa documents late Badenian age in the D and R samples and an 87Sr/86Sr age of 13.54 Ma (13.39–13.7 Ma) published by Hudáčková et al. (2003).

The most detailed paleoecological analyses have been done for ZT nannoplankton assemblages (Figs. 3, 7, 11) with common R. haqii, followed by C. pelagicus, indicating a nearshore nutrient-rich environment. Higher values of R. haqii/C. pelagicus ratio (Supplement 1) point to warmer stratified (stressed) waters with reduced upwelling (Báldi-Béke 1984; Andreeva-Grigorovich 1998; Auer et al. 2014; Ivančič et al. 2018). Associations from ZT10, 12, 15 (Fig. 8a) generally dominate along continental margins, indicating a strong influx of terrigenous material and relative proximity to the shore (Haq 1980; Aubry 1992). An influx of terrigenous material mixed with freshwater (brackish—B. b. bigelowii) may have resulted in the reworking of older taxa (sensu Ćorić and Hohenegger 2008; Auer et al. 2014). Association in ZT5 is equitable and transitional toward the third cluster (Fig. 8a). Cluster 3 with H. macroporus and low values of sphenoliths and rare discoasters indicate a cooling trend (Perch-Nielsen 1985; Lehotayová 1989; Spezzaferri and Ćorić 2001).

The correlation of nannofossil assemblages from localities along Malé Karpaty Mts. (ZT, J, K, BAZ, VH, R) shows variability in its origin. Small- and medium-sized reticulofenestrids dominate ZT samples (Fig. 8b) with higher SSD (Supplement 1) reflecting temperate water with nutrients derived from the coast. In contrast, cluster 3 with J and K with the prevalence of C. pelagicus reflects nutrient-rich stable upwelling waters (Cachão and Moita 2000; Jamrich and Halásová 2010; Auer et al. 2014). Cluster 2 (Fig. 8b) with BAZ, R1, R2, VH5 documents less nutrient-warmer conditions which is in accordance with NMDS analysis (Fig. 9). PCA biplot analysis (Fig. 10b) from the combined dataset, together with published data (Jamrich and Halásová 2010; Hyžný et al. 2012), shows the most decisive influence within samples (most of D, ZT10, S1-1) by R. haqii reflecting a more open sea, stress environment conditions. The associations of S, ZT5, 8, 12, J, K, D are dominated by C. pelagicus, reflecting cold waters and upwelling. Increased availability of terrigenous nutrients and stable water conditions (Haq 1980; Cachão and Moita 2000; Wade and Bown 2006; Ćorić and Hohenegger 2008; Auer et al. 2014) with prevalence of R. minuta (D, ZT9, 11, 15, 17, J, BAZ, VH, R) indicate warm water (Rahman and Roth 1990). NMDS analysis of this dataset proves equal distribution of the studied assemblages (Fig. 10a).

The obtained results are tied to paleogeography (Fig. 18) from the Devínska Kobyla Hill to Rohožník. The paleoenvironment of the Devín area (DSi, DZ, ZT, L, G, MQ) is interpreted as a bay-lagoon system. Water temperature varies from warmer stratified or mixed temperate to cooler depending on the currents. Terrigenous input and upwelling currents are the primary sources of nutrients. The paleoenvironment of the Sandberg area (lower part with massive bioturbated sandstone facies; Sm; Fig. 2) indicates shallow marine conditions under fairweather wave base but still with higher energy with normal salinity, warmer waters than mid-outer shelf upwelling influenced mudstones. The lower sequence passes into a low-energy environment Sfm in the upper part. The uppermost part of the limestone facies is characterized by corallinacean limestones representing a change in the sedimentation. Warm water nutrient tolerant C. macintyrei, Discoaster variabilis, H. carteri, H. wallichii, U. jafari, S. abies are documented in Sm and Sfm facies. Algal limestone facies yield a low diversified cosmopolitan nannoplankton, possibly due to low nutrient supply. The scarcity of planktonic foraminifers is caused by coast proximity.

Fig. 18
figure 18

a The late Badenian paleogeographic block diagram of the Vienna Basin’s eastern margin suggest the original distribution of the Sandberg Fm. limestones. Explanatory notes: RV—Rohožník Vajarská, RK—Rohožník Konopiská, J—Jabloňové Sandpit, SC—Stupava clay pit, VH—Stupava-Vrchná hora, ZB—Záhorská Bystrica proposed landfill shallow wells, BAZ—Bratislava automobile works, D—Devínska Nová Ves clay pit, S—Devínska Nová Ves Sandberg, FL—Devínska Nová Ves Fuchs quarry, MQ—Devín Medieval quarry, ZT—Devín Zelené Terasy, DZ—Devín Záhrady, DSi—Devín Šibeničný vrch, L—Devín Lingula bed, G—Devín Glossus bed; b a schematic paleogeographic map (after Rybár et al. 2016) of the Vienna and Danube basins demonstrating the inflow of normal marine water (blue arrows) from the “Trans-Tethyan Trench Corridor” (Piller et al. 2007) that supports carbonate growth. It also shows the entry points for clastic sediments (yellow lines) that inhibit carbonate growth. The study area is highlighted in red. c Paleogeographic map of the Paratethys Sea (Studencka et al. 1998; Popov et al. 2004; Bartol et al. 2014; Palcu et al. 2017), with the area of interest in red square; d distribution map of the upper Badenian limestones and evaporites in/around the Pannonian Basin System. The map indicates areas where carbonate growth was promoted and areas where carbonate growth was hindered due to evaporite precipitation or clastic input (after Steininger et al. 1985; Hámor and Halmai 1988; Peryt and Kasprzyk 1992; Pisera 1996; Sachsenhofer et al. 1998; Popov et al. 2004; Brânzilă and Chira 2005; Harzhauser et al. 2014, 2019, 2020; Hohenegger et al. 2014; Báldi et al. 2017; Kováč et al. 2017a, b, 2018a, b; Pavelić and Kovačić 2018, Mandic et al. 2019a, b; Piller et al. 2022; Babinszki et al. 2023; Piller and Harzhauser 2023)

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Distally, temperate deeper waters with cooler episodes in D are supported by nannoplankton (H. macroporus) and foraminifera. Mass occurrence of G. bulloides and T. quinqueloba (D, ZB) documents temperate and cold water (Hilbrecht 1996) that rapidly responds to an increase in nutrient supply (Reynolds and Thunell 1985). Nearshore affinity and warmer indices (D. altispira) are documented only in the BAZ, coinciding well with the dominance of reticulofenestrids. Northeastwards located VH shows a nearshore environment as mentioned from S, with limestone facies. Further north, a different nearshore paleoenvironment is at J and K (Sm and Sfm facies), documented on the prevalence of C. pelagicus and Globigerina sp. div. reflecting cooler eutrophic and upwelling conditions. The most northeast sites are RV and RK. Limestone facies present in RV is similar to S. From RK (Fm facies), a rich plankton assemblage with T. trilobus and O. universa documents temperate warm waters further away from the coast.

The detailed analysis from the Devín area (DZ, ZT, L, G) reveals (1) well-oxygenated, euryhaline shallow (e.g., inner, mid-outer shelf) normal marine water conditions, (2) deeper normal marine (e.g., shelf-break slope) water with reduced oxygen content on the seafloor (Fig. 18a), (3) eutrophic normal marine deeper waters (e.g., shelf-break slope).

In the upper part of the ZT I profile (Figs. 2, 3, 18a), an autochthonous mass abundance of Bu. elongata (Figs. 11, 12, Supplement 2), usually indicating deep-water conditions (Fontanier et al. 2002), is here preserved in a generally shallow water (Švagrovský 1981; Hyžný et al. 2012) paleoenvironment depleted in oxygen (Kaiho 1994; Báldi and Hohenegger 2008; Kranner et al. 2021b). Cimerman et al. (1988) document the mass occurrence of Bulimina in shallow water conditions (water depth ca. 42 m) with low oxygen like the ZT I profile.

Dysoxic conditions in the Devín area are supported by Varicorbula gibba, which thrives well under such conditions and is present in ZT, DZ, G (Hyžný et al. 2012). Varicorbula is a typical opportunistic colonizer of disrupted habitats with a reduced number of accompanying taxa, which can quickly become a dominant faunal element (Hoffman 1977, 1979; Mandic and Harzhauser 2003). It is usually distributed from low intertidal zones to considerable depths of several hundred meters (Švagrovský 1981; Salas 1996). Significant abundances of V. gibba in subtidal muds in the northern parts of the VB could point to unstable conditions (Mandic and Harzhauser 2003; Fuksi et al. 2016; Soliman et al. 2023). A strongly stratified water column in the system of narrow channels and protected lagoons can be the reason for the emergence of such communities. A shallow water shelf environment with increased temperatures, and thus also salinity increase will enable the seawater to be supersaturated by CO32− (Morse et al. 2007), leading to calcium carbonate precipitation. Such conditions are supported by the dominance of Amphistegina, which is associated with algal limestones (Hallock 1985) visible in ZT, L, S, J, K, RV. Well-aerated oligotrophic shallow water with seagrass or rigid substrate suitable for algal patch reef growing is observed in upper Badenian strata today exposed on the Malé Karpaty Mts. slopes (S, F, VH, K, J, RV). Algal limestone with Lithothamnion remnants in life position is documented in S, RV, VH (Schaleková 1969, 1973; Hrabovský and Fordinál 2013; Pivko et al. 2017) and in the ZT, BAZ, J the algal limestone clasts are also present (this study; Figs. 3, 4, 6, 19). Coccolith crusts document an oligotrophic environment and low terrigenous input on foraminifera tests from BAZ (Fig. 11). A similar situation but with high productivity is mentioned by Vlček et al. (2022).

Fig. 19
figure 19

Lithothamnion limestones thin sections. a Lobatula lobatula, S; b Borelis melo, S; c Textularia bocki, S; d Pseudotriloculina cf. consobrina, MQ; e Quinqueloculina cf. seminulum, MQ; f Elphidium crispum, MQ; g Lithothamnion limestone thin section, VH; h Amphistegina mamilla, Quinqueloculina sp. indet, VH; i Lithothamnion limestone thin section, RV; Borelis melo (yellow arrows); j Borelis melo, Spiroloculina sp. indet., RV; k Cycloforina badenensis, gastropod indet., RV

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Significant change in the sediment is documented by benthic assemblage, which varies from mud–silty mud, sand, to limestone. A muddy bed is documented by infaunal genera such as Bolivina and Bulimina, together with Melonis in the westernmost part of the Devínska Kobyla slopes (DZ, ZT, G) and D, Záhorská Bystrica (JV) situated further from the seashore. Sandy seabed covered by seagrass is documented by the prevalence of epiphytic taxa such as Biasterigerina, Amphistegina, and keeled elphidia in the localities nowadays in a higher position on the foothills of Devínska Kobyla and Malé Karpaty Mts. (L, FL, S, K, J). Algae reef (carpets and patches) was identified based on the algae buildups and abundant miliolids (B. melo) at various localities from Devínska Kobyla—S, VH, R (Fig. 19). Apart from changes in substrate type, there were also changes in oxygen level and nutrient supply. Low oxygen levels correlate well with fine, muddy sediment, especially in open sea environments identified from D, ZB, RK in nowadays different positions. We have identified former bays (Fig. 18a) on the western slopes and central part of Devínska Kobyla Hill (G, ZT, L) with a low oxic and cold-water environment in the shallow water sediment on the presence of Bulimina–Bolivina together with C. laevigata associations. Stratified water column with freshwater input is indicated by warmer and lower salinity tolerant taxa B. bigelowii (Bartol et al. 2008), small reticulofenestrids from ZT and G together with the absence of planktonic foraminifera.

Palynology

Palynology analysis of the studied area shows different coastal vegetation types. Samples ZT4, ZT6, ZT7 reflect an almost marginal depositional environment, shallow water with local swamps, and diversified terrestrial pollen flora (Supplement 4). The zonal vegetation elements indicate a humid subtropical climate. Very good preservation of palynomorphs indicates dysoxic conditions in the depositional system. Well-preserved marine palynomorphs occur in ZT5 and ZT11. Samples ZT8–10, ZT12, ZT14–16 reflect an oxic environment or taphonomic processes that led to the degradation of organic matter and reflect environmental dynamics, such as mechanical damage and sorting or the original size of the clasts. The association from D is dominated by Pinaceae and Fagaceae, what represents riparian forests and swamps together with extrazonal mountain vegetation (Supplement 4). Zonal vegetation reflects subtropical to warm-temperate humid climate. S, BAZ, ZB, VH were barren of palynofossils due to unfavorable conditions of the coastal sediments (Sm facies).

Data from the upper part of ZT profile (ZT4–6) can be correlated with data published by Sitár and Kováčová-Slamková (1999). The dinoflagellate cysts assemblage from ZT correlates well with the upper Badenian association described by Soliman et al. (2023) reflecting marine, tropical to warm-temperate climate conditions.

Discussion

Four distinct, genetically diverse lithofacies delineate the upper Badenian paleoenvironments of the VB eastern margins (Slovakia). While these lithofacies are widely recognized, they have yet to be comprehensively described and defined individually. In the Slovak part of the VB, the Studienka Fm. is characterized by massive to laminated mudstones, indicative of a mid-outer shelf to deep basin setting. This facies is also evident in archived data (Čierna 1973; Šujan et al. 1992; Hudáčková and Kováč 1993; Kováčová and Hudáčková 2009; Jamrich and Halásová 2010; Fuksi 2012). Support for the deep-water nature of this facies comes from seismic reflection data, which reveals prograding oblique clinoforms that are hundreds of meters thick (Kováč et al. 2004; Paulissen and Luthi 2010; Paulissen et al. 2011; Lee and Wagreich 2017; Kranner et al. 2021a; Csibri et al. 2022). Based on the classification scheme by Pellegrini et al. (2020), these clinoforms can be categorized as part of the shelf-break slope environment. In the Austrian part of the basin, this facies is referred to as the Rabensburg Fm. (Harzhauser et al. 2020). Described facies exhibit a lateral transition to massive muddy and sandy facies with a ~ 3:1 ratio, as identified by this and previous studies (e.g., Kováčová and Hudáčková 2009; Fordinál et al. 2012; Hyžný et al. 2012). These sediments have been classified as deep basin facies up to fossiliferous mudflats and lagoons (Harzhauser et al. 2020), correlating with outer to inner shelf settings. Examples of these facies can be found in the present study, specifically at the Zelené terasy I, III, IV and in numerous archived studies describing sections and shallow wells at the eastern VB margin (Fordinál et al. 2012). Meanwhile the shallow water facies are still commonly referred to as the Studienka or Rabensburg fms. (Harzhauser et al. 2020; Harzhauser 2022a, b, c; Kranner et al. 2021a), it is recommended that the shallow water facies should be defined as separate member or formations due to their distinct genetic environment.

The shallow water muddy facies may be transitional to facies dominated by sands, featuring uni-directional (Březina et al. 2021) to bi-directional (Ruman et al. 2017) cross-beds and clinostratified, unsorted conglomerate bodies (Nehyba and Roetzel 2004; Baráth 2009). These facies are associated with alternating terrestrial (fluvial and alluvial fans) and shallow marine environments (wave and tide-dominated coast) (Pivko et al. 2017; Ruman et al. 2017). The sandy facies might exhibit heavy bioturbation, which is so pronounced that the primary structures are disintegrated, which results in their massive appearance. Such facies have been documented in this study, for example, at the Jabloňové sandpit, as well as in archived studies from the Devínska Kobyla Hill (Hyžný et al. 2012). Both marine and terrestrial macrofauna are found, including the famous remains of hominids (Holec and Emry 2003). Baráth (1993) proposed a separate member within the Studienka Fm. for these facies, referred to as the Sandberg Mb.

However, the issue arises because the member includes mudstones, sandstones, conglomerates, and limestones. To avoid conflicts with the nomenclature, defining two genetically different shallow water upper Badenian fms. is essential (lateral equivalents of Studienka/Rabensburg Fm.): 1 clastic Stupava Fm., 2 limestone Sandberg Fm.

Definition of the Stupava Formation:

Derivation of name: Named after the town near Bratislava, “Stupava town.”

Synonyms: Stupava Mb.; Láb Amphistegina sands (horizon) (Fordinál et al. 2012; Hrabovský and Fordinál 2013).

Type section: The peak of Vrchná hora Hill, located near Stupava (48°15′39.34′′ N, 17° 2′48.39′′ E) is in the VB, Záhorie lowland, Slovakia. The site placed SE of Stupava above the gardening area was initially referenced by Fordinál et al. (2012) and was subsequently described in greater detail by Hrabovský and Fordinál (2013).

Thickness: The thickness spans several tens of meters, as corroborated by multiple composite outcrops scattered around the hill`s summit (Hrabovský and Fordinál 2013).

Lithology: The Stupava Fm. is characterized by the abundance of massive sands and sandstones, with the sandstones frequently displaying trough and planar cross-bedding patterns. This Fm. includes dominant white or light-yellow sandy components. In addition, the Fm. encompasses massive and laminated sandy mudstones, with limestone clasts being a notable constituent within the sandy strata. While the primary lithology of the Stupava Fm. is consistent, it occasionally presents more diverse rock types, including massive or graded conglomerates of varying sizes and compositions, often dominated by bioclasts. Moreover, massive or laminated mudstones are observed, but less frequently than the predominant sand and sandstone layers.

Biostratigraphy/fossils: The Stupava Fm. is rich in calcareous nannofossils (C. miopelagicus, C. macintyrei, H. walbersdorfensis, H. wallichii, P. japonica, S. abies); benthic foraminifers (B. melo, Miniacina miniacea, A. mammilla, E. aculeatum, B. maxima, Bu. intonsa, G. bulloides, T. quinqueloba); gastropods (Turritella tricarinata); bivalves (Cubitostrea digitalina, Paroxystele orientalis, F. leythajanus, Oppenheimopecten aduncus; polyplacophorans; corals; bryozoans; serpulids; echinoderms; ichnofossils; coralline algae (Lithothamnion, Lithophyllum, Titanoderma) (this study, see Supplements 1, 2, 5 in detail).

Depositional environment: The typical depositional depth ranges from ~ 20–50 m (Hrabovský and Fordinál 2013; Pivko et al. 2017; this study). The depositional environment corresponds to a shallow marine setting on the inner shelf, predominantly influenced by tidal and wave actions along the coast. From a sedimentary perspective, it is inferred that the depth did not exceed the normal wave base, with an upper limit ~ 0 m and a lower limit ~ 60 m (bathymetric determination derived from Pellegrini et al. 2020).

Age: Middle Miocene (late Badenian; early Serravallian); younger than 13.8–13.6 Ma up to ~ 12.7 based on NN6 Zone correlation.

Chronometry: Fordinál et al. (2014) reported 87Sr/86Sr ages of 13.4–12.8 Ma (Stupava-Vrchná hora) and 13.12–13.02 Ma (Sandberg section).

Overlying unit: The Stupava Fm. crops out on steep hillside inclinations, typically overlaid by the Sandberg Fm. In subsurface instances, the Stupava Fm. is covered by the upper Badenian Sandberg Fm. and by sandy and muddy Holíč and Skalica fms. of Sarmatian age (Vass 2002; Hyžný et al. 2012; Fordinál et al. 2013; this study).

Lateral equivalents: The Rabensburg and Studienka fms., as noted in the Austrian and Slovak territories, signify muddy counterparts within a basinal context (Vass 2002; Fordinál et al. 2013; Harzhauser et al. 2020, 2022). Laterally, the Stupava Fm. sandy facies can transition into shallow water limestones, identified as the Sandberg Fm. (see below), as supported by the present study findings.

Geographic distribution: The Stupava Fm. type area is located around the western hill slopes of the Malé Karpaty Mts. (Hrabovský and Fordinál 2013; this study; Figs. 2, 3, 6). The Stupava Fm. also appears along the northern margin of Devín (Hyžný et al. 2012; Pivko et al. 2017; Ruman et al. 2017; this study).

Outcrops: Devín—Zelené Terasy, BAZ, Jabloňové (all in this study), Devín—Medieval quarry (Pivko et al. 2017), Sandberg, DNV—Fuchs quarry, Devín—Šibeničný vrch (all from Hyžný et al. 2012), Devín—Záhrady (Ruman et al. 2017), Stupava-Vrchná hora (Hrabovský and Fordinál 2013).

Definition of the Sandberg Formation:

Derivation of name: Named after the hill near Bratislava, “Sandberg Hill.”

Synonyms: Limestones of the Sandberg Mb. (Baráth 1993; Vass 2002; Fordinál et al. 2012), St. Margarethen Limestone Harzhauser et al. (2020); Harzhauser (2022a, b, c) and Rákos Limestone of Császár (1997).

Remarks: Certain instances of the Sandberg Fm., particularly at Stupava (Hrabovský and Fordinál 2013), are occasionally misclassified as part of the Leitha Fm. (Harzhauser et al. 2020). This classification is incorrect, given that the Sandberg Fm. dates to the late Badenian (~ 13.8–12.7 Ma) and is correlated with the lower part of NN6 Zone (present study). This implies only a minor overlap (between 13.8 and 13.6 Ma) with the Leitha Fm., which is older and correlated with the NN5 Zone (Wiedl et al. 2013). The minor discrepancy is caused by the NN5/NN6 zonal boundary being set to 13.65 Ma while the Langhian/Serravallian is set to 13.82 Ma Gradstein et al. (2020).

Type section: The summit of the historical Sandberg sandpit near Bratislava (48°12′03′′ N, 16°58′29′′ E) is in the VB, Záhorie lowland, Slovakia. The Sandberg sandpit is accessible and constitutes a portion of the protected Sandberg—Pajštún Geopark. This section was first described in detail by Švagrovský (1981), then subsequently amended by Baráth (1993), and later biostratigraphically supplemented by Hyžný et al. (2012).

Thickness: As reported by Švagrovský (1981) and Hyžný et al. (2012), the Sandberg Fm. reaches a maximum thickness of 19 m, as evidenced by outcrop data obtained from the western slopes of the Malé Karpaty Mts.

Lithology: The Sandberg Fm. comprises white to cream-colored or light-yellow organodetritic limestones, occasionally featuring coquina-oyster beds. Locally porous, these limestones are filled with cavities resulting from the leaching of gastropod and bivalve shells. Foraminiferal tests and corals may also be present. The Fm. also includes sandy organodetritic limestones with muddy admixtures (Schaleková 1969, 1973, 1978; Benejová 1985; Hladilová 1991; Fordinál et al. 2012; Hrabovský and Fordinál 2013; Zlinská and Madarás 2014).

Biostratigraphy/fossils: The Sandberg Fm. is exceptionally rich in fossils. Calcareous nannofossils (C. macintyrei, H. wallichii, S. abies); benthic foraminifers (A. mammilla, Elphidium crispum, B. melo); echinoids; bryozoans; brachiopods; gastropods (Turritella tricarinata, Paroxystele orientalis); bivalves; polyplacophorans; coralline algae (Lithothamnion, Lithothamnion minervae, L. ramosissimum, L. valens, L. corallioides, Phymatolithon calcareum, Spongites albanensis, Mesophyllum, Lithophyllum, Sporolithon, Titanoderma pustulatum, Hydrolithon) (this study, see Supplements 1, 2, 5 in detail).

Depositional environment: Shallow marine, inner shelf carbonate ramps, coral carpets, and seagrass meadows. The typical depositional depth ranged from ~ 10 to 30 m (Pivko et al. 2017) to ~ 20–50 m (Hrabovský and Fordinál 2013).

Age: Middle Miocene (late Badenian; early Serravallian); younger than 13.8–13.6 Ma based on NN6 Zone correlation.

Chronometry: Fordinál et al. (2014) reported 87Sr/86Sr ages of 13.4–12.8 Ma from the Stupava-Vrchná hora and 12.8–12.6 Ma or 12.7 Ma.

Overlying unit: The Sandberg Fm. typically forms surface outcrops on steep hill slopes, resulting in the erosion of overlying units in most cases. In subsurface occurrences, the Sandberg Fm. is overlain by muddy and sandy Sarmatian deposits from the Holíč and Skalica fms. (Vass 2002; Hyžný et al. 2012).

Lateral equivalents: The Rabensburg and Studienka fms. represent muddy equivalents across Austrian and Slovak territories in basinal and shallow water settings (Vass 2002; Fordinál et al. 2013; Harzhauser et al. 2020; Harzhauser 2022a, b, c). These facies may be a transition to shallow water and alluvial sands and conglomerates.

Geographic distribution: The Sandberg Fm. type area is located around the western margin of the Malé Karpaty Mts (Fig. 18). These outcrop occurrences are delimited to the west by the approximately NE–SW striking Láb fault line, which extends from Lozorno in the south to Rohožník in the north (Schaleková 1969, 1973, 1978; Benejová 1985; Hladilová 1991; Hrabovský and Fordinál 2013) but they were identified in the deep well Kúty-45 (489–515 m, Kováč et al. 2008a, b) too. The Sandberg Fm. also appears along the northern margin of Devín district (Pivko et al. 2017).

Outcrops: Devín—Zelené Terasy II (this study), DNV—Bratislava automobile works BAZ (this study), DNV—Sandberg sandpit (Hyžný et al. 2012), Devín—Medieval quarry (Pivko et al. 2017), Stupava-Vrchná hora section (this study, new biostratigraphy), and (Hrabovský and Fordinál 2013), Rohožník—Vajarská (Schaleková 1973; Hladilová 1991).

Upper Badenian limestone deposition in the Central Paratethys

During the late Badenian in the CP, the Badenian Salinity Crisis led to the formation of extensive evaporite deposits, primarily gypsum/anhydrite and halite, as highlighted by de Leeuw et al. (2018). These deposits are predominantly found in the Carpathian Foredeep (Pisera 1996; Bąbel and Bogucki 2007) (Fig. 18d), the Transcarpathian (Galamay and Karoli 1997; Vass et al. 2000; Túnyi et al. 2005), and the Transylvanian basins (Krézsek et al. 2010; Beldean et al. 2012). In contrast, the VB and the Pannonian Basin show gypsum/anhydrite in smaller amounts, mostly in cuttings and core samples (Harzhauser et al. 2018, 2020; Kováč et al. 2007; Báldi et al. 2017). These evaporites are intercalated with algal limestones, a pattern seen in the Carpathian Foredeep (Studencki 1979; Peryt and Kasprzyk 1992; Pisera 1996; Szczechura 2000; Brânzilă and Chira 2005; Studencka and Jasionowski 2011). In the Vienna and Pannonian basins, evaporites are less common, blending with muddy and sandy facies, but algal limestones are well developed (Pisera 1996; Magyar et al. 2006; Malvić and Velić 2011; Rundić et al. 2011; Harzhauser et al. 2019, 2020; Piller et al. 2022; Babinszki et al. 2023; Piller and Harzhauser 2023; this study). The Styrian and Danube basins, free from evaporites of this period, feature coralline limestones (Pisera 1996; Schreilechner and Sachsenhofer 2007; Kováč et al. 2018a, b), possibly due to the late Badenian flooding event (Piller et al. 2007). This indicates a deep, broad connection to the global ocean with minimal clastic interference. Thus, basins across the CP, exhibit varying degrees of sea way restriction, ranging from minor (Vienna, Pannonian basins) to major (Carpathian Foredeep, Transcarpathian, and Transylvanian basins), leading to partial or complete circulation cut-offs and subsequent evaporite precipitation. Notably, in the Transylvanian (Krézsek et al. 2010; Beldean et al. 2012) and Transcarpathian basins (Vass 2002), the absence of thick algal limestone deposits suggests presence of significant terrigenous input (e.g., Vass 2000; Klčovo delta) directly above the evaporites, inhibited algal limestone growth. This pattern underscores a dichotomy in the CP basins: some dominated by carbonate growth and others by evaporite deposition.

Conclusion

Our investigation has deployed an integrative approach, employing multiple proxy records, including calcareous nannoplankton, foraminifera, sedimentology, and palynology, to analyze outcrop data of upper Badenian (Serravallian) sediments from the Paratethys Sea shelf. Biostratigraphic dating was conducted based on the presence of O. rugosus (ZT9–12, 17, J9), a common occurrence of H. walbersdorfensis (ZT5, 8, 9, 11, K1), and the absence of S. heteromorphus (observed as reworked in J4, J7). O. universa (D, RK) supports these results and aligns with the NN6/CPN9 zones. Our findings accentuate the utility of taphonomic processes and paleoecological proxies for fine-scale characterization and detecting minor fluctuations in paleoenvironmental conditions. One of our key findings is that the distinctive bioherm structures discovered have facilitated the description of limestone formation within the VB (Sandberg Fm.). These limestones are most likely not restricted to the local environment but appear widespread throughout the CP region. The evidence collected supports a substantial connection between the Mediterranean and CP through the Trans-Tethyan Trench Corridor, with the connectivity being strengthened by upwelling conditions observed along the eastern margin of the VB.

Furthermore, our research confirms two primary mechanisms that hindered carbonate growth in the CP area during the late Badenian. The first mechanism was a substantial influx of siliciclastic material from the Alps and Carpathians, resulting from the ongoing rifting of the Vienna and Danube basins. The second mechanism was the initiation of evaporite precipitation in the Transcarpathian and Transylvanian basins, which interrupted normal carbonate growth. In conclusion, this study underlines the crucial interplay between regional geodynamic processes and carbonate sedimentation during the Middle Miocene.