Foraminiferal and Palynological Records of an Abrupt Environmental Change at the Badenian/Sarmatian Boundary (Middle Miocene): A Case Study in Northeastern Central Paratethys

: The Badenian/Sarmatian boundary in the Central Paratethyan basins is characterised by a change from open marine conditions during the late Badenian to the assumed brackish conditions during the early Sarmatian. The foraminiferal and palynological results of the Badenian/Sarmatian boundary interval in the Babczyn 2 borehole (in SE Poland) showed that the studied interval accumulated under variable, unstable sedimentary conditions. The Badenian/Sarmatian boundary, as correlated with a sudden extinction of stenohaline foraminifera, is interpreted as being due to the shallowing of the basin. The lack of foraminifera and marine palynomorphs just above the Badenian/Sarmatian boundary can reflect short-term anoxia. The composition of the euryhaline assemblages, characteristic for the lower Sarmatian part of the studied succession, indicates from marine to hypersaline conditions.


Introduction
The largest faunal turnover event in the Paratethys-a large epicontinental sea extending from Central Europe to inner Asia since the Oligocene [1]-occurred in the Middle Miocene at the Badenian/Sarmatian boundary, when 94% of Badenian species became extinct (Badenian-Sarmatian Extinction Event-BSEE; [2]).It was proposed that the cause of this event was a drastic basin-wide change in water chemistry from open marine conditions during the late Badenian to brackish conditions in the Central Paratethyan basins during the early Sarmatian.The details of this transformation are still under discussion, though [3,4] concluded that there is no evidence of shallowing associated with the BSEE.Ref. [5] suggested that because of a complex tectonic evolution, the closure of the Paratethyan basins at the end of Badenian was most probably diachronous, and, thus, slightly different ages for the Badenian/Sarmatian boundary across the Paratethys should be expected.
This study presents foraminiferal and palynological results of the upper Badenian-Sarmatian strata in one borehole section in Poland, namely, Babczyn 2, located in the northeastern part of the Carpathian Foredeep, which is the largest Central Paratethyan Basin (Figure 1).The aim of this study was to identify environmental changes around the inferred Badenian/Sarmatian boundary.The studied borehole is a key section of the northern marginal part of the Carpathian Foredeep [3,[6][7][8].A recent biostratigraphic study of two boreholes, including Babczyn 2 [8], confirmed, in general, zonation based on foraminifera that was previously established within the Badenian and Sarmatian strata of the northern margin of the Carpathian Foredeep [9][10][11][12][13] (cf.[14]; Figure 1).In the upper Badenian, the lower Neobulimina longa Zone and the upper Cibicides crassiseptatus (Hanzawaia crassiseptata) Zone occur (Figure 1); the latter is considered to be synchronous with the Velapertina indigena (Łuczkowska) planktonic foraminiferal zone [15].

Geological Setting
The Carpathian Foredeep basin developed in front of the West Carpathians in the Early Miocene and is subdivided into inner and outer parts [20].The fill is mostly composed of Middle Miocene (Badenian and Sarmatian) deposits.The Badenian and Sarmatian strata in this northern marginal part are several hundred metres thick, and towards the axial part of the Carpathian Foredeep, their thickness increases to more than 4 km.
The Langhian red-algal limestones and quartz arenites of the Pi ńczów Formation (Figure 1) originated from shelf and near-shore environments, and mudstones and clays originated from more basinal locations (e.g., [21]).Their thickness in the Babczyn 2 borehole is approximately 12 m.These are overlain by the Serravallian gypsum of the Krzy żanowice Formation [22] deposited during the Badenian Salinity Crisis ( [23], with references therein).The gypsum sequence is 32 m thick [6].In the uppermost part, an intercalation (2.3 m thick) of marly clays with marine palynomorphs (dinoflagellate cysts) and foraminiferal assemblages occurs [7].It originated from a short-lived marine transgression to the Badenian evaporite basin prior to the transgression re-installing normal marine conditions in the Carpathian Foredeep Basin, which resulted from the reconnection of the basin with the Mediterranean and Eastern Paratethys primarily by tectonic modification of the interconnecting gateways [24].
Consequently, the Serravallian gypsum is overlain by the sandy-silty series of the Machów Formation (Figure 1).Its upper Badenian part is referred to as the Pecten Beds [25].They are, in turn, overlain by Syndesmya Beds, which were considered to be Sarmatian by [25].Ref. [3] confirmed the location of the Badenian-Sarmatian boundary between the Pecten and Syndesmya Beds at the highest occurrence of well-preserved and identifiable pectinid shells.The location was 6.0 m above the Babczyn Tuff found in the middle portion of the Pecten Beds and 3.4 m above the gypsum, which constrained its depositional age to 13.06 ± 0.11 Ma [3].This age was calibrated against the same astronomically tuned FC standard (e.g., [24]), giving an age of 13.41 ± 0.10 Ma, which was comparable to the age of 13.32 ± 0.07 Ma recorded for a volcanic ash layer located several metres above the Badenian evaporites in the Romanian East Carpathians [24].This recalibrated age was used as shown in Figure 1.
The Syndesmya Beds form the lowermost part of the Krakowiec Clays ( [26,27], with references therein; Figure 1).Ref. [8] proved that the Badenian-Sarmatian boundary lies within the Syndesmya Beds (Figure 1) and not at their base as previously was assumed.The thickness of the Machów Formation in the Babczyn 2 borehole is almost 400 m; however, only the lowermost part of the formation was cored, and its coring started at a depth of 350 m [25].
For palaeoecological analysis, species or groups of species that exceeded 5% in at least one sample were taken into account.There is a direct relationship between the abundance of species within a community and the environment.Abundance fluctuations of benthic foraminifera are sensitive palaeoceanographic indicators responding to changing palaeotemperature, salinity, nutrient supply, and oxygen conditions.
For palynology, 26 samples were studied (i.e., the odd sample numbers from 9 to 55 and the even numbers 8 and 28).The applied palynological procedure included 38% hydrochloric acid (HCl) treatment, 40% hydrofluoric acid (HF) treatment, heavy-liquid (ZnCl 2 + HCl; density 2.0 g•cm −3 ) separation, ultrasonication for 10-15 s, and sieving at 10 µm on nylon mesh.No nitric acid (HNO 3 ) treatment was applied.Each processed rock sample weighed 10 g.Two slides from each sample were prepared using glycerine jelly as a mounting medium.The same set of slides was used for the analyses of dinoflagellate cysts, palynofacies (P.G.), and sporomorphs (E.W. and G.W.).Unprocessed rock samples, palynological residues, and slides were stored in the collection of the Institute of Geological Sciences at the Polish Academy of Sciences Research Centre in Kraków, Poland.The most common and characteristic species are illustrated in Figures 5 and 6, respectively.
A Zeiss Axiolab microscope equipped with 20× lens and 100× oil lens was used for the analyses of the palynofacies and dinoflagellate cysts.The quantitative dinoflagellate cyst analysis was conducted by counting about 300 specimens; in lower-frequency cases, all the specimens from both prepared slides were counted.On this basis, the Shannon-Wiener diversity index (H ′ ) was calculated as follows: H ′ = −∑p i ln(p i ), where p i is the relative abundance of each taxon and is expressed as e H ′ .The most frequent and important taxa for palaeoenvironmental reconstructions were grouped into eight dinoflagellate cyst morphogroups as follows: • Spiniferites morphogroup, including all the Spiniferites and Achomosphaera specimens; • Batiacasphaera morphogroup, including B. sphaerica, Batiacasphaera sp.
The palynofacies analysis was performed by counting 500 particles.The palynofacies elements in the present study were assigned to nine groups as follows:  Black, opaque phytoclasts representing the most resistant coalified land plant remains;  Dark-brown phytoclasts, which are land plant remains, usually equidimensional, translucent (or with translucent edges), remaining in structureless wood or cortical tissues;    The palynofacies analysis was performed by counting 500 particles.The palynofacies elements in the present study were assigned to nine groups as follows:

•
Foraminifera organic linings (zooclasts), which are the organic cells of foraminifera; • Amorphous organic matter (AOM), which represents structureless particles of uncertain origins (most likely marine origin in the case of the present study materials), representing a stage in the bacterial decay of organic particles in oxygen-depleted environments.
The identified sporomorph taxa were classified based on the Atlas of Pollen and Spores of the Polish Neogene [53][54][55][56].In the studied material, the following palaeofloristical elements were distinguished: "palaeotropical" (P), including "tropical" (P1) and "subtropical" (P2); "arctotertiary" (A), including "warm-temperate" (A1) and "temperate" (A2); and cosmopolitan (P/A).The data from the palynological spectra were used to construct a palynological diagram.In the diagram, the percentage shares of the pollen and spore taxa were calculated from the total sum of the pollen grains and spores, and the proportion of non-pollen palynomorphs was computed separately in relation to the total sum using POLPAL software [57].
Microphotographs of the selected sporomorphs and fungal palynomorphs (Figure 6) were obtained using a Nikon Eclipse E400 microscope equipped with a Canon A640 digital camera.
In the Badenian part of the studied succession comprising the Pecten Beds and lowermost part of the Syndesmya Beds, both planktonic and benthic foraminifera occur.However, in sample 9, the tests of the foraminifera are damaged in most cases, indicating their transportation and reworking.Sample 10 possesses almost entirely planktonic foraminifera; rare specimens of benthic foraminifera were recorded.Samples from 11 to 28 yielded abundant and well-preserved foraminiferal assemblages, and sample 29 is almost devoid of foraminifera.Upsection, the samples from 30 to 35 from the lowermost Sarmatian yielded only benthic foraminifera, and in the upper part of the section (samples from 35 to 55), foraminifera are rare, and their assemblage is composed of miliolids and reworked forms from the Badenian.Only in a short interval (samples from 47 to 49), the abundant assemblage of miliolids occurs, and in samples 50 and 51, Bolivina sarmatica with miliolids is recorded.Owing to small numbers of specimens, quantitative analysis was not performed for the upper part of the studied section.

Palynofacies
All the samples yielded palynological organic matter, the elements of which showed various ratios reflecting variable environmental conditions and/or various sedimentological processes (Figure 8).The palynofacies of the studied samples were dominated by terrestrial elements represented by palynodebris (black and dark-brown phytoclasts and cuticles) and pollen grains.The shares of these two groups showed variable proportions: palynodebris (cuticles in particular) dominated in the lower part of the studied interval and decreased moving upwards, being replaced by pollen grains in the middle part and AOM in the upper part (Figure 8).
The proportion of marine elements (dinoflagellate cysts-Figure 5, prasinophytes, acritarchs, and rare zooclasts) rarely exceeded 10%.Dinoflagellate cysts were the most common in the lower and middle intervals while becoming rare or absent in the upper Assemblage I occurs at the base of the section (sample 8); sample 9, because of large numbers of resedimented specimens, has not been taken into account (Figure 7).This assemblage is characterised by the dominance of Bulimina (30%) and Uvigerina (30%).Other important components are Angulogerina, which exceeds 17%, and Bolivina (10%).Subsidiary species include Melonis pompilioides, Globocassidulina subglobosa, Astrononion perfossum, Asterigerinata planorbis, and Lobatula lobatula.The P/B ratio exceeds 60%; the H(S) diversity index is 2.5.Infaunal taxa comprise 95% of the assemblage.
Assemblages III and IV alternate twice in the middle and upper parts of the Pecten Beds.They differ from the under-and overlying assemblages by a complete lack of Uvigerina.Instead, Angulogerina angulosa is one of dominant taxa and forms from 12% to 28% of these assemblages.

Palynofacies
All the samples yielded palynological organic matter, the elements of which showed various ratios reflecting variable environmental conditions and/or various sedimentological processes (Figure 8).The palynofacies of the studied samples were dominated by terrestrial elements represented by palynodebris (black and dark-brown phytoclasts and cuticles) and pollen grains.The shares of these two groups showed variable proportions: palynodebris (cuticles in particular) dominated in the lower part of the studied interval and decreased moving upwards, being replaced by pollen grains in the middle part and AOM in the upper part (Figure 8).
AOM occurred in two samples from the middle part of the studied interval (samples 29 and 31) and in the upper part, where it dominated in some samples (Figure 8).

Dinoflagellate Cysts
Virtually all the studied samples (except for samples 29, 31, and 45) involved dinoflagellate cysts.A total of 44-48 taxa assumed to be in situ were distinguished.We note that some taxa, such as Spiniferites ramosus s.l., included several species and/or subspecies, which were not distinguished for the purposes of the present study (Tables 1-4).Despite this apparent taxonomical richness, the taxonomic diversity of the dinoflagellate cyst assemblages was low, and it oscillated between 2.0 and 6.5 (Figure 9).The majority of the samples yielded assemblages dominated by from three to four species, with the remaining taxa being represented by rare or even single specimens.The dominant taxa included Spiniferites ramosus s.l., Batiacasphaera spp., and Systematophora The proportion of marine elements (dinoflagellate cysts-Figure 5, prasinophytes, acritarchs, and rare zooclasts) rarely exceeded 10%.Dinoflagellate cysts were the most common in the lower and middle intervals while becoming rare or absent in the upper part, where prasinophytes and acritarchs predominated among the aquatic palynomorphs (Figure 8).
AOM occurred in two samples from the middle part of the studied interval (samples 29 and 31) and in the upper part, where it dominated in some samples (Figure 8).

Dinoflagellate Cysts
Virtually all the studied samples (except for samples 29, 31, and 45) involved dinoflagellate cysts.A total of 44-48 taxa assumed to be in situ were distinguished.We note that some taxa, such as Spiniferites ramosus s.l., included several species and/or subspecies, which were not distinguished for the purposes of the present study (Tables 1-4).Despite this apparent taxonomical richness, the taxonomic diversity of the dinoflagellate cyst as-semblages was low, and it oscillated between 2.0 and 6.5 (Figure 9).The majority of the samples yielded assemblages dominated by from three to four species, with the remaining taxa being represented by rare or even single specimens.The dominant taxa included Spiniferites ramosus s.l., Batiacasphaera spp., and Systematophora spp., with the most common ones being Operculodinium spp.and Lingulodinium machaerophorum; their proportions varied from sample to sample and could also be different in neighbouring samples.Some species, like Nematosphaeropsis labyrinthus, Selenopemphix nephroides, Reticulatosphaera actinocoronata, Lingulodinium machaerophorum, and Polysphaeridium subtile, showed increased frequencies only in single samples.The highest diversity values, between 4.5 and 6.5, were recorded in the lower studied interval, which included the upper Badenian (samples 8-27, except for samples 17 and 25).The diversity decreased in the succession, above the two barren samples (29 and 31), where it oscillated between 2.3 and 4.5 (with a minimal diversity of 0.5 being recorded in sample 51).However, this decreasing upwards diversity trend was not gradual; a characteristic feature was that the diversity in the assemblages from the subsequent samples was alternately higher and lower, thereby forming the zigzag course of the chart (Figure 9).The diversity in dinoflagellate cyst assemblages was generally correlated with the number of taxa.The highest numbers of dinoflagellate cysts (15)(16)(17)(18)(19)(20)(21)(22) were recorded in the lower part of the studied interval (samples 9-27).The numbers of taxa from the higher interval were lower, oscillating between 4 and 7, with higher values (i.e., 11, 13, and 16) being present only in three samples (37,35, and 49, respectively, Figure 9).the upper interval (Table 1); the only exception was their common occurrence in sample 51, which yielded the most taxonomically impoverished assemblage (Figure 9).Representatives of the Operculodinium morphogroup occurred in all the positive samples except for sample 33, taken just above the two barren samples; their proportions were not high, i.e., rarely exceeding 20% (Figure 9).They showed a negative correlation with the Batiacasphaera morphogroup, similar to representatives of the Spiniferites morphogroup (Figure 9).
Representatives of the Systematophora morphogroup were rare or absent in the lower and middle parts of the studied borehole interval while becoming more frequent in the higher part, starting from sample 41.Their proportions in this interval oscillated between 30 and a bit over 60% (except for sample 51).The proportions of Systematophora were negatively correlated with those of Batiacasphaera (most visible in sample 51) and Lingulodinium (samples 39 and 51) and showed a positive correlation with Polysphaeridium (Figure 9).The representatives of the latter were very rare or absent except for two samples (33 and 37), which yielded approximately 46 and 18%, respectively.The Lingulodinium share was similar; it was infrequent or absent, being a dominant taxon (almost 80%) in sample 39.
Nematosphaeropsis labyrinthus was a very rare species throughout the studied borehole interval; it occurred infrequently in only four samples from the basal part (Table 1).However, it formed an acme in sample 27, collected below the barren interval (samples 29 and 31), where it reached almost 40% of all the dinoflagellate cysts.Another characteristic feature of the dinoflagellate cyst assemblages from the studied borehole interval was the predominance of gonyaulacoids.Most of the studied samples yielded purely gonyaulacoid assemblages.Peridinioids were represented by Selenopemphix and Lejeunecysta; the latter and S. brevispinosa occurred mainly as single specimens only in a few samples (Tables 1, 2 and 4), whereas S. nephroides formed an acme in sample 41 (up to 25% of the whole assemblage, Figure 9).
The diversity and frequency of the taxa in the studied materials were related to the frequencies of some taxa grouped into eight morphogroups.Representatives of the Spiniferites and Batiacasphaera morphogroups were the most common taxa in the lower part of the studied succession (samples 8-28).Their frequencies showed a negative correlation: samples with common Spiniferites yielded few Batiacasphaera, whereas increased frequencies of Batiacasphaera were associated with decreased Spiniferites (Figure 9).This relationship was further correlated with changes in diversity in this interval; Batiacasphaera-dominated assemblages (samples 17, 21, and 25) showed the lowest diversities.Representatives of the Batiacasphaera morphogroup were virtually absent in the upper interval (Table 1); the only exception was their common occurrence in sample 51, which yielded the most taxonomically impoverished assemblage (Figure 9).
Representatives of the Operculodinium morphogroup occurred in all the positive samples except for sample 33, taken just above the two barren samples; their proportions were not high, i.e., rarely exceeding 20% (Figure 9).They showed a negative correlation with the Batiacasphaera morphogroup, similar to representatives of the Spiniferites morphogroup (Figure 9).Representatives of the Systematophora morphogroup were rare or absent in the lower and middle parts of the studied borehole interval while becoming more frequent in the higher part, starting from sample 41.Their proportions in this interval oscillated between 30 and a bit over 60% (except for sample 51).The proportions of Systematophora were negatively correlated with those of Batiacasphaera (most visible in sample 51) and Lingulodinium (samples 39 and 51) and showed a positive correlation with Polysphaeridium (Figure 9).The representatives of the latter were very rare or absent except for two samples (33 and 37), which yielded approximately 46 and 18%, respectively.The Lingulodinium share was similar; it was infrequent or absent, being a dominant taxon (almost 80%) in sample 39.
Nematosphaeropsis labyrinthus was a very rare species throughout the studied borehole interval; it occurred infrequently in only four samples from the basal part (Table 1).However, it formed an acme in sample 27, collected below the barren interval (samples 29 and 31), where it reached almost 40% of all the dinoflagellate cysts.
The Impagidinium morphogroup occurred in the basal part of the studied borehole interval (only one specimen was found in the remaining part, sample 49).The distribution of very uncommon specimens of Impagidinium showed a pattern similar to that of Nematosphaeropsis (Figure 9).

Other Aquatic Palynomorphs
Dinoflagellate cysts were not the only aquatic palynomorphs found in the studied borehole interval.Other aquatic palynomorphs occurred in all the samples while reaching even higher frequencies in some of them.These included acritarchs (e.g., Veryhachium, Nannobarbophora, and unidentified small, sphaeromorphic, spiny, and smooth forms); prasinophytes (e.g., Tasmanitaceae and Leiosphaeridiaceae); and zooclasts (foraminifera organic linings, scolecodonts, and remains of presumably arthropods).The diversity of other aquatic palynomorphs exhibited high variability from sample to sample, thereby resembling the distribution pattern of dinoflagellate cyst assemblages.
The lowermost sample (No. 8), yielded frequent Leiosphaeridiaceae (described below as the genus Leiosphaeridia, although its precise taxonomic position is tentative).Samples 9-13 yielded foraminifera organic linings and Nannobarbophora.Tasmanites co-occurred with Nannobarbophora in sample 15 and Leiosphaeridia in sample 17.Neither sample yielded foraminifera organic linings; these were found in sample 19 (with frequent Nannobarbophora and rare Leiosphaeridia).The latter had an increased frequency in the subsequent sample, sample 21, which yielded no Nannobarbophora and only single foraminifera organic linings.The frequency of Leiosphaearidiaceae in higher samples showed a fluctuating course: it decreased in sample 23, increased in sample 25, and decreased again in sample 27, whereas the occurrences of Tasmanites and Nannobarbophora in these samples showed the opposite trend.Sample 27 also yielded Veryhachium.Rare Tasmanites and Veryhachium were the only prasinophytes and acritarchs, respectively, in sample 28.
The distribution patterns of acritarchs and prasinophytes in the lower part of the studied borehole interval (samples 8-28) showed specific patterns that were further correlated with dinoflagellate cyst assemblages.There was a clear negative correlation between the assemblages dominated by foraminifera organic linings and Nannobarbophora (and Tasmanites to a lesser degree) and those dominated by Leiosphaeridia.Moreover, the samples that yielded the former assemblages yielded relatively diverse dinoflagellate cyst assemblages.These samples, which yielded impoverished assemblages dominated by Batiacasphaera, also exhibited increased frequencies of Leiosphaeridia.
Various spherical forms attributed to Leiosphaeridiaceae became the nearly sole aquatic palynomorphs in samples 29 and 31, which yielded no dinoflagellate cysts; scolecodonts were found in sample 31.Leiosphaeridia were again dominant in the subsequent sample (33), which yielded impoverished dinoflagellate cyst assemblages with relatively frequent Polysphaeridium.
Higher intervals of the studied borehole (samples 35-55) yielded common to very common Leiosphaeridiaceae, represented by morphologically diversified forms, some of which likely represent sphaeromorphic, smooth acritarchs.They were predominant in these samples over other prasinophytes, and acritarchs were commonly the only aquatic palynomorphs (other than dinoflagellate cysts).Rare Nannobarbophora occurred in samples 35, 37, and 49, and a single foraminifera organic lining was found in sample 51.
Reworked dinoflagellate cysts commonly occurred in the lower part of the studied borehole interval (samples 8-28).These were Palaeogene specimens representing mainly Eocene-Oligocene forms, and the Palaeohystrichophora found in sample 27 may have been Cretaceous forms.Higher borehole intervals yielded much less frequently reworked specimens, which were mainly Cretaceous forms (Tables 1-4; reworked taxa are highlighted with an asterisk).

Spore-Pollen Analysis
All the samples yielded pollen grains and spores suitable for palynological analysis.In most samples, 300-500 pollen grains and spores (a minimum of 100 in sample 21) were identified.Besides sporomorphs, all the co-occurring non-pollen palynomorphs in the samples were counted.Most sporomorphs were poorly preserved; however, they were still identifiable.A total of 71 fossil-species (including nine species of plant spores, 16 species of gymnosperm pollen, and 46 species of angiosperm pollen) were identified (Table 5).In all the samples, among the pollen grains of the gymnosperms, bisaccate pollen grains (Figure 6C) of the Pinaceae family (mainly Pinus, plus Cathaya, Abies, Picea, Keteleeria/Pseudolarix, and Cedrus); Taxodium/Glyptostrobus (Figure 6D); Tsuga (Figure 6E,F); and Sciadopitys (Figure 6G,H) were the most common.Additionally, several pollen grains of Sequoia/Sequoiadendron/Metasequoia/Cryptomeria were encountered (Figure 10).

Spores
Fern spores were also rare, with the Baculatisporites, Laevigatosporites, Leiotriletes, Neogenisporis (Figure 6B), and Verrucatosporites fossil genera being present.In contrast, spores of Sphagnum (Figure 6A) were encountered in all the samples.Several lycopod spores (related to the modern genera Lycopodium and Lycopodiella) were also recorded.Typical freshwater algae were virtually absent, and only scarce Botryococcus colonies were encountered.Microremains of fungi (Figure 6P,Q) were continually found in the palynological profile.Fungal spores were present in all the samples, whereas sporocarps were mainly present in the upper section of the profile (Figure 10).

Aquatic Palaeoenvironment
The qualitative and quantitative analyses of the foraminifera and aquatic palynomorphs showed that the studied borehole interval accumulated under variable, unstable sedimentary conditions (Figure 11).
broadly overlapping distributions and occupied a niche similar to that of Orbulina in the surface waters [48].The ratio between the planktonic and benthic foraminifera (P/B) is related to the water depth, and the percentage of planktonic foraminifera generally increases with increasing distance from the shore.However, next to the water depth, the oxygen level of the bottom water has profound effects on the abundance and diversity of benthic foraminifera.This significantly influences the percentage of planktonic foraminifera in assemblages [50].According to the foraminiferal trophic condition and oxygen concentration (TROX) model [71], the benthic foraminifera distribution is a function of the interplay between the food availability and oxygen concentrations.The dominance of infaunal species is interpreted as an indicator of an increase in the organic matter supply and the dominance of the eutrophic and dysoxic environments.In oligotrophic and welloxygenated environments, assemblages are dominated by epifaunal species [29,72].The variations in the proportions of epifaunal and infaunal species indicate distinctive inputs of organic matter (phytodetritus input versus bacterial activity, respectively) [73].
Benthic foraminiferal assemblages from the Badenian part of the studied section (Assemblages from I to VI) are dominated by deep infaunal buliminids (Bulimina) and shallow infaunal uvigerinids (Uvigerina and Angulogerina).Melonis and Sphaeroidinashallow infaunal species-as well as epifaunal Cibicidoides, Hanzawaia, and Heterolepa are common components of benthic foraminiferal assemblages.The high dominance of

Foraminiferal Record
Foraminifera are commonly used as proxies for palaeoenvironmental studies because of the correlation between foraminiferal test shapes and their palaeoenvironmental requirements [32,58].Planktonic foraminifera can be useful indicators of ancient sea-level changes because of their depth stratification [44, 59,60].The vertical distribution of planktonic foraminifera is directly related to their life cycle.They reproduce at species-specific depths relative to the pycnocline and under distinct temperature and salinity conditions; thus, they require a water column at certain depths for ontogenetic vertical migration and reproduction [60,61].Simple morphologies (r-strategists), which are representative of the most cosmopolitan and opportunistic taxa, inhabit shallow, more nutrient-rich, eutrophic waters [62,63].Planktonic foraminifera in the upper Badenian part of the succession included Globigerina (with Globigerina bulloides being dominant within this group) and rarely recorded Trilobatus and Velapertina.Globorotalia, which shows preferences for deeper/intermediate habitats, was not recorded in the studied succession.Globigerina bulloides reproduces primarily within the upper 60 m of the water column and exhibits the maximum abundance at this depth [60,[64][65][66].It is also considered to be an indicator of cooler [67,68] and nutrient-rich eutrophic waters [44,62,69,70].Velapertina was endemic to the Central Paratethys, where it appeared to have repeated the same sequence of transitional steps as Orbulina [48].The two genera had broadly overlapping distributions and occupied a niche similar to that of Orbulina in the surface waters [48].
The ratio between the planktonic and benthic foraminifera (P/B) is related to the water depth, and the percentage of planktonic foraminifera generally increases with increasing distance from the shore.However, next to the water depth, the oxygen level of the bottom water has profound effects on the abundance and diversity of benthic foraminifera.This significantly influences the percentage of planktonic foraminifera in assemblages [50].According to the foraminiferal trophic condition and oxygen concentration (TROX) model [71], the benthic foraminifera distribution is a function of the interplay between the food availability and oxygen concentrations.The dominance of infaunal species is interpreted as an indicator of an increase in the organic matter supply and the dominance of the eutrophic and dysoxic environments.In oligotrophic and well-oxygenated environments, assemblages are dominated by epifaunal species [29,72].The variations in the proportions of epifaunal and infaunal species indicate distinctive inputs of organic matter (phytodetritus input versus bacterial activity, respectively) [73].
Benthic foraminiferal assemblages from the Badenian part of the studied section (Assemblages from I to VI) are dominated by deep infaunal buliminids (Bulimina) and shallow infaunal uvigerinids (Uvigerina and Angulogerina).Melonis and Sphaeroidina-shallow infaunal species-as well as epifaunal Cibicidoides, Hanzawaia, and Heterolepa are common components of benthic foraminiferal assemblages.The high dominance of infaunal taxa (>95%), mainly buliminids and uvigerinids (Assemblage I) in the lowermost part of the studied interval (samples from 8 to 10), indicates a large supply of organic matter to the sea floor, the dominance of eutrophic conditions, and the oxygen impoverishment of the bottom waters in this area.In the basal part of the studied interval, benthic foraminifera were very rare in sample 10 (Figure 7).Their absence can be explained by a short episode of dysoxic conditions at the bottom of the sea at this site.
The gradual increase in epifauna up the section from 20% in Assemblage II to almost 40% in Assemblage VI indicates a change from eutrophic to mesotrophic conditions, a decrease in the organic matter supply, and an amelioration in oxygen in the bottom waters.
The alternation in the assemblages dominated by infaunal and shallow infaunal taxa, Bulimina, Angulogerina, and, to lesser degrees, Bolivina (Assemblages III, IV, and VI) and Uvigerina (Assemblages II and V), may be the result of slightly different requirements in the types of food and oxygen levels of each taxon.In the uppermost Badenian (samples from 11 to 28), the contribution of the infaunal taxa decreases, and diversity increases, which suggest mesotrophic conditions in the surface waters and increased oxygenation in the bottom waters.
There is also one more factor that could influence the composition of benthic foraminiferal assemblages.Middle Miocene tectonic activity in the Carpathian Foredeep [74] resulted in intensive volcanism with enhanced input of volcanoclastic material [3,75].Studies and monitoring of the changes in the compositions of benthic foraminiferal assemblages from the South China Sea following the 1991 Mt. Pinatubo eruption have revealed that high tephra settling rates through the water column led to the mass mortality of benthic biota and to significant survival and rapid recovery of the ecosystem in distal parts of the ash fan, where the thickness of the ash layer did not exceed a few millimetres [76,77].
The Badenian/Sarmatian boundary, as correlated with a sudden extinction of stenohaline foraminifera (BSEE), is placed just above sample 28 (within the lowermost part of the Syndesmya Beds; Figure 7).The overlying sample (29) is almost barren of foraminifera from both groups, planktonic and benthic ones.Higher up in the section, assemblage VII is dominated by elphidiids alternating with assemblage VIII, which is dominated by miliolids.These groups of foraminifera are euryhaline and can tolerate a wide range of salinities from brackish to elevated.Keeled species of Elphidium prefer inner-shelf environments characterised by salinities of 30-70‰ and 0-50 m water depths.At this site, they are represented only by very rare specimens of Elphidium fichtelianum and E. macellum.Unkeeled species occur in brackish-hypersaline marshes and lagoons showing salinity ranges of 0-70‰ [29,38].In the studied section, they are represented by Elphidium excavatum, E. angulatum, E. advenum, and E. hauerinum.Miliolids (Quinqueloculina and Triloculina) occur in hypersaline marine environments (salinity ranging from 32 to 55-65‰), mainly in hypersaline lagoons or on the marine inner shelf [29,78].The replacement of stenohaline foraminiferal assemblages by euryhaline ones indicates a salinity increase, while the disappearance of planktonic foraminifera suggests a shallowing of the sea.
The next almost monospecific assemblage (assemblage IX), which is dominated by Anomalinoides dividens, probably reflects a salinity lowering to normal marine values.Presently, marine environments are characteristic for Anomalinoides [79], although in the past, its wider environmental range, including brackish salinity conditions, was accepted [46] (with references therein).

Palynomorph Record
The presence of marine palynomorphs suggests that most of the studied section accumulated in marine environments.However, changes in palynofacies and the compositions of aquatic palynomorph assemblages among particular samples suggest that these environmental conditions were unstable while being subjected to numerous changes related to sea-level fluctuations, salinity, and climatic changes.All these factors may have played important roles in the aforementioned changes in aquatic assemblages.
Undoubtedly, the lower part of the studied borehole interval (samples 8-28; the Pecten Beds and the lowermost part of the Syndesmya Beds) accumulated in a marine environment influenced by runoff from the neighbouring land.The upward-decreasing proportions of cuticles suggest that land influences were gradually decreasing; the simultaneous increase in pollen grains (Figure 8) confirms this interpretation, as most of the grains were bisaccate forms, which are airborne, and can be transported for long distances (the so-called 'Neves effect'; see, e.g., [80,81]).However, there were no other signs of land influences, such as a salinity decrease; there were neither freshwater algae nor dinoflagellate cysts, which prefer low-salinity waters.Despite the relatively intense land influence, this interval was presumably deposited under relatively offshore conditions compared with the interval above sample 28.Only this interval yielded Impagidinium and Nematosphaeropsis, two dinoflagellate cyst genera commonly associated with offshore waters (e.g., [82][83][84]), while the upper interval yielded only a single Impagidinium (sample 49; Table 1).
The interval below the Badenian/Sarmatian boundary (samples 17-28) showed a series of environmental fluctuations manifested by alternating changes in aquatic palynomorph compositions.High-diversity marine palynomorph assemblages dominated by Spiniferites alternated with less-diverse Batiacasphaera-dominated assemblages.Moreover, Nematosphaeropsis labyrinthus occurred during this interval and exhibited a negative correlation with Batiacasphaera (Figure 9).
Spiniferites (mainly S. ramosus and the morphologically similar Achomosphaera) occurs in a broad marine environmental spectrum and is commonly treated as a cosmopolitan taxon (e.g., [82]).But several authors, such as in [85,86], have suggested that its frequency increases offshore.It is also present in the marine Middle Miocene strata of the Carpathian Foredeep and is the most frequent in marine shelf environments (e.g., [87]).This suggests that the samples that yielded diversified assemblages (with frequent Spiniferites) represent strata accumulated in a marine environment, representing an offshore setting, in contrast to those that yielded impoverished assemblages with common Batiacasphaera.Although the latter genus was described by [88] as a Batiacasphaera micropapillata complex, including B. micropapillata and B. minuta, as is typical for outer neritic to oceanic waters with slightly increased salinities, Batiacasphaera (mainly B. sphaerica) tends to exhibit increased frequencies in restricted environments possibly associated with water shallowness and/or increased salinity [87,89].The negative correlation between Batiacasphaera and Nematosphaeropsis labyrinthus may be an additional clue suggesting sea-level fluctuations during this period.However, Nematosphaeropsis labyrinthus is treated as a cold-water species (e.g., [90]) in contrast to Batiacasphaera, which is believed to be a temperate-to warm-water taxon [88].This suggests that an acme of N. labyrinthus just below the Badenian/Sarmatian boundary may be the result of a temperature drop in sea-surface waters (a similar inverse correlation between N. labyrinthus and Batiacasphaera micropapillata was noted by [91] and was interpreted as a possible cooling).Notably, high frequencies of N. labyrinthus were found in the Pecten Beds overlying the Badenian evaporites in the Carpathian Foredeep [92].This might indicate a cooling period (or periods) after the accumulation of the evaporitic series.However, N. labyrinthus is known to be found in warm-water middle Badenian Korytnica Clays and their offshore age equivalents-the Skawina Beds [87,89].
The interval that occurred just above (samples 29 and 31) was characterised by a lack of dinoflagellate cysts and the flowering of Leiosphaeridiaceae.Any of the aforementioned environmental factors-albeit at a larger magnitude-could be the one that led to such a drastic environmental change in the earliest Sarmatian, associated with the collapse of the dinoflagellate floras.The precise reconstruction of environmental changes during the accumulation of these strata is difficult.The absence of dinoflagellate cysts (Figure 8) indicated disastrous conditions for dinoflagellate cysts.However, the most likely reason was that the salinity increased above the tolerable level, even for hypersaline forms (e.g., Polysphaeridium) but was still favourable for Leiosphaeridia.This Prasinophyta genus (e.g., [93]) was described in the Carpathian Foredeep, more specifically, in the middle Badenian evaporitic strata accumulated under increased water salinity conditions (e.g., [89]) and in upper Badenian stress deposits [94].These possible hypersaline conditions were associated with stagnant, possibly stratified, waters that led to anoxic conditions in the bottom waters, as evidenced by AOM (Figure 8).Hypersaline waters are usually stagnant.If waters are affected by strong circulation, particularly in a deeper basin, then hypersalinar conditions are less likely to appear.The Palynological record shows blooms of Leiosphaera, a prasinophyte alga widespread in the Miocene salt deposits of the Carpathian Foredeep, simultaneously with the appearance of amorphous organic matter (AOM), which is typical for anoxic bottom conditions.We have no indications as to the precise salinity level (certainly above 3.5%).
The cessation of these conditions was caused by a possible sea-level rise and the gradual return of a less-saline water regime.The latter interpretation is supported by the fact that sample 33 yielded a high frequency of Polysphaeridium (a genus known to exist in hypersaline environments, e.g., [95]), which benefited from the transitional salinity levels between the highly saline conditions that were disastrous for the genus (samples 29 and 31) and the conditions that prevailed during the accumulation of the higher interval (samples 35 and above).Polysphaeridium was described at a similar position, i.e., in the strata directly overlying the chemical deposits in other areas of the Miocene of the Carpathian Foredeep (e.g., [94,[96][97][98]).
The higher interval (samples 35-55, i.e., the upper part of the Syndesmya Beds and the overlying part of the Krakowiec Clays; Figure 9) was deposited under more restricted and variable environmental conditions (compared to those of the basal interval, namely, samples . This interval yielded no offshore species (except for a single Impagidinium specimen in sample 49), and the diversity and number of taxa decreased significantly (Figure 9).However, the factors responsible for these conditions remain unclear.There were no clear indicators of sea-level or salinity changes.An important event was the disappearance of Batiacasphaera, which can be interpreted either as the result of cooling or changes in sea-water chemistry; however, its nature remains uncertain.A drop in the sea-surface water temperature is also suggested by the lack of Nannobarbophora gedlii, which is believed to be a warm-water species [99].
Some recorded events may indicate fluctuations in the salinity level.There are almost no stenohaline foraminiferal organic linings (present in the lower interval, namely, samples 8-28), and some taxa known to benefit from low-salinity, commonly nutrient-rich waters, show temporarily enriched frequencies (e.g., [84]).These include Lingulodinium machaerophorum and heterotrophic Congruentidiaceae (peridinioids are represented in the present material by Selenopemphix and Lejeunecysta).L. machaerophorum dominated sample 39, whereas rare peridinioids occurred in the top interval (samples 39-55), forming an acme of Selenopemphix in sample 41 (Table 4; Figure 9).This interval, in turn, was preceded by samples 33 and 37, which yielded Polysphaeridium-a hypersaline taxon (see above).Another characteristic feature of the strata above the Syndesmya Beds was the common occurrence of Systematophora.This genus was missing or rarely exceeded 10% in the lower interval, whereas it accounted for over 40%, maximally over 60%, in some samples from the upper interval (Figure 9).However, palaeoenvironmental preferences of Systematophora are poorly understood.Ref. [86] included Systematophora placacantha in the Glaphyrocysta eco-group, which included open-marine (i.e., fully marine) and warm-water taxa.Ref. [82] highlighted the widespread occurrence of this genus and linked it to shelf environments in any climatic setting.The analysis of Systematophora (S. placacantha and S. ancyrea) occurrences in the Miocene of the Carpathian Foredeep shows a broad environmental tolerance range of this genus, as it is a member of fully marine (e.g., [87,100]) and impoverished assemblages (e.g., [92]).However, a noticeable feature of the occurrence of this genus is the remarkable frequency increase in Sarmatian deposits (e.g., [92]), which may be linked to the euryhaline nature of this genus.A similar acme of Systematophora (as Clesitosphaeridium) was noted in the uppermost Badenian-lower Sarmatian Paratethyan deposits in Hungary [101].
Another clue suggestive of fluctuating, mainly restricted, environments during the accumulation of the upper part of the Syndesmya Beds and the Krakowiec Clay is the persistent presence of Leiosphaeridia (and presumably some other sphaeromorphic, smooth acritarchs).Their occurrence may reflect not only salinity fluctuations (see above) but also generally cooler surface waters and/or increased nutrient availability (see [91], p. 55 and references therein).
An exception was an assemblage yielded from sample 51, i.e., a low-diversity assemblage dominated by Batiacasphaera, with no peridinioids.Its palynofacies is also exceptional as it includes no AOM in contrast to the remaining samples from this interval.The appearance of Batiacasphaera may be related to the temporal return of fully marine conditions, possibly because of a short-term sea-level rise.The AOM that occurred in most of the samples from this interval indicates stagnant waters with a low oxygen content in the bottom environments.Even a low-magnitude sea-level rise could induce sea-water circulation and better ventilation at the bottom.The appearance of Batiacasphaera in sample 51 may also reflect an increase in surface sea-water temperatures.

Terrestrial Palaeoenvironment
Although some sporomorphs are corroded, the palynological analysis provided valuable information about the palaeovegetation, palaeogeography, and palaeoclimate.The degree of pollen grain destruction can also be used as a source of information.For example, some bisaccate pollen grains were heavily corroded, particularly in samples with high marine palynomorph contents (at the lower part of the section; Figure 10).This pollen could have easily been transported over long distances, from both the northern seashores and the Carpathians, and their abundance tends to increase offshore (the so-called 'Neves effect').Nevertheless, conifers likely played an important role in the coastal forests.For example, the better-preserved non-bisaccate pollen grains of Tsuga and Sciadopitys were the most likely components of mesophytic forests in the vicinity.In the upper section of the profile (above sample 27), some pollen grains were found in clumps (Ericaceae, Fagus, and Salix), which may also indicate the proximity of their habitats to the coast.
The results of the palynological analysis revealed the presence of mesophytic and wetland vegetation along the Paratethys shoreline during sedimentation.Mesophytic forests were composed of Fagus, Quercus (also thermophilous oaks producing pollen of the fossil-species Quercoidites henricii), Tsuga and other conifers, Carpinus, Tilioideae, and others, with a relatively small admixture of Castaneoideae and other thermophilous taxa.Ulmus, Pterocarya, Carya, Zelkova, Liquidambar, Alnus, Acer, Fraxinus, and Salix probably grew in riparian forests in periodically flooded areas, such as river valleys.Taxodium and/or Glyptostrobus, together with Alnus and Nyssa, were likely elements of swamp forests growing in permanently flooded areas in the vicinity.Similarly, Osmunda and other ferns grew in wet places.Various shrubs of the Ericaceae family, as well as Myrica and Ilex, probably were components of shrub communities.The abundance of ericaceous plants may be related to open areas adjacent to the coastline within coastal peat bogs or heathland-type shrub vegetation and partly with forest undergrowth [102,103].Herbs were represented mainly by the Cyperaceae, Sparganiaceae/Typhaceae, and Poaceae families, and at least some of them could have grown in freshwater margins (e.g., Cyperaceae, Sparganium, and/or Typha).The presence of numerous pollen grains of Chenopodiaceae coincides with the occurrence of high-salinity habitats, such as seashores, because many of the recent species of this family are halophytes that tolerate salty soils.
The changes in the frequency of the spore-pollen taxa were rather small, and no rapid change in vegetation was observed.Nevertheless, the lower section appeared richer in "palaeotropical" taxa (Ilexpollenites margaritatus, Symplocoipollenites vestibulum, and Tricolporopollenites indeterminatus), although it generally had a high content of marine palynomorphs, and the land elements have had little chance of reaching this location.In contrast, the upper section contained more diverse Pinaceae pollen grains, including Abies and Picea, which can be interpreted as a manifestation of the mountain forest development.Such changes are gradual and modified by the changing sea influences; therefore, a boundary between the levels cannot be set.
Diverse fungal microremains (i.a., Asterosporium, Cephalothecoidomyces, Diporotheca, Phragmothyrites, Potamomyces, and cf.Tetraploa) were found, mainly in the upper part of the profile.Their presence indicated a brackish environment and their proximity to the seashore.Cephalothecoidomyces G. Worobiec, Neumann, and E. Worobiec and Potamomyces K.D. Hyde suggest that abundant decaying wood could have accumulated in humid and swampy places [104][105][106].Contemporary Diporotheca webbiae D. Hawksworth., B. van Geel, and P. Wiltshire, similar to the fossil specimen from Babczyn, is associated with alder carrs [107].Therefore, it is probable that the coastal areas, at least in some parts, were overgrown by swamp forests, as also indicated by the studied fossil pollen grains.The co-occurrence of the fossil conidia of the Asterosporium asterospermum (Pers.)Hughes fungus with Fagus pollen grains indicates that beech trees grew close to the seashore [108].
The results of the palynological analysis indicated that the climate during the deposition of the sediments was generally warm temperate (warmer than the present-day climate of Poland), mild (without severe winters), and rather humid.Some fungal taxa (notably Potamomyces and probably Tetraploa) indicated a humid and warm, subtropical climate during this period [104,106,109].
Miocene sediments in Poland have a relatively rich palynological documentation, but most studies come from the Polish Lowlands [110,111].In contrast, palynological (spore-pollen) studies of the Carpathian Foredeep are rare.Moreover, Badenian-Sarmatian marine sediments that were previously analysed were mainly from the western, Silesian region of the Carpathian Foredeep [110,[112][113][114][115]. In addition, palynofloras from several boreholes in the Bochnia and Wieliczka regions [116], including borehole Kłaj 1 [117], as well as from the sulphur deposits at Piaseczno near Tarnobrzeg [102], were studied.Although the frequency of sporomorphs in these deposits was usually low, the samples usually had similar compositions, exhibiting abundant conifers with high levels of Pinus as well as Abies, Tsuga, and Picea.Among the deciduous trees, Quercus, Ulmus, Castanea, Engelhardia, and Fagus played the most significant roles, whereas Carya, Pterocarya, and Tricolporopollenites pseudocingulum (in some cases identified as Rhus) were less important.Shrubs and thermophilous ferns were also relatively frequent.Swampy plants, which are characteristic of continental sediments in the Polish Lowlands, were rare (except for Taxodium/Glyptostrobus) and included only taxa, such as Alnus, Liquidambar, Myrica, and Ilex [103].
The Babczyn palynoflora is very similar to the spore-pollen assemblage from the Jamnica S-119 borehole [103] drilled in the upper Badenian and lower Sarmatian marine deposits near Tarnobrzeg in the northeastern part of the Carpathian Foredeep.The Jamnica palynoflora was dominated by coniferous trees, especially Pinus, as well as Tax-odium/Glyptostrobus (identified as Taxodiaceae-Cupressaceae), Tsuga, Abies, Picea, Cedrus, and Sciadopitys, whereas the pollen of Sequoia was identified only in some samples.Among deciduous trees and shrubs, Ulmus, Quercus, Alnus, Carya, Fagus, Ericaceae, Engelhardia, Pterocarya, and Quercoidites henricii were the most frequent.Some samples frequently contained small percentages of tree and shrub taxa, such as Betula, Carpinus, Liquidambar, Salix, Acer, Castanea, Fraxinus, Juglans, Nyssa, Parrotia, Myrica, Symplocos, Cyrillaceae/Clethraceae, Ilex, and Tricolporopollenites pseudocingulum.Pollen grains of herbaceous plants were very rare, with sporadic Chenopodiaceae, Cyperaceae, Poaceae, Lamiaceae, and Nuphar.Similarly, the spores of ferns (Polypodiaceae, Osmunda, and Cyatheaceae-Schizaeaceae) and Sphagnum appeared in very small quantities.The composition of plant communities in the entire Jamnica section was quite homogeneous, and no temporal flora changes were observed.The highest content of pollen material was in the middle part of the Jamnica profile, with more abundant pollen from deciduous trees and herbaceous plants, accompanied by a simultaneous decrease in Pinus, which indicated the more landward position of that part of the profile.Differences in the pollen spectra from Jamnica may suggest a shoreline migration at this level rather than changes in palaeovegetation caused by the climate [103].
Ref. [118] made similar assumptions for the entire Carpathian Region.Their palaeofloristic and palaeoclimatic reconstructions showed that the upper Badenian and lower Sarmatian floras were closer to each other than to the flora of the previous and subsequent stages.The evolutionary process during the late Badenian-early Sarmatian continued the main trends of forest floral and vegetational evolutions, stimulated by the gradual cooling of the climate [119].At this time, the replacement of the subtropical forest communities by warm temperate and temperate forest communities was observed in the Central Paratethys.In the southeastern part of Ukraine (Eastern Paratethys), temperate forests were replaced by herb communities.This process was evident in all the studied sections, albeit involving spatial differences [118,120,121].

Implications
Although a consensus exists that at the Badenian-Sarmatian boundary, a sudden decrease in biodiversity and the disappearance of marine foraminifer assemblages in the Central Paratethys occurred (e.g., [122]), there are various hypotheses regarding its drivers.Ref. [123] concluded that this change occurred within a time interval of fewer than 10 kyr and that it was related to a change in the configuration of the Central-Eastern Paratethys gateway (Bârlad Strait).It could also have been related to a minor rise in the global sea level that otherwise affected the Sarmatian transgression in many other basins of the Central Paratethys ( [124], with references therein).Ref. [125] suggested a continuous sea level rise in the Eastern Paratethys because of freshwater input by rivers, and, thus, the Sarmatian transgression event could have resulted from a full connection between both Paratethyan basins.It was repeatedly suggested that the transgression was accompanied by a drastic change in water chemistry, exemplified by a supposed change from marine to brackish conditions in the Central Paratethys (cf.[16,126]), which otherwise could be expected considering the inflow of Eastern Paratethyan water to the Central Paratethys.
Ref. [16] concluded that tectonic widening and the deepening of the Bârlad Strait generated an effective water exchange between the two domains.However, our data do not support the brackish-water environments at the onset of the Sarmatian, as envisaged by [16,123,127].Instead, the domination of the foraminiferal assemblages above the Badenian/Sarmatian boundary by miliolids, which is commonly observed in various parts of the Carpathian Foredeep Basin in Poland [8,14], implies from normal to hypersalinity conditions lower than 50 psu [29,128].As far as the palynological record on the onset of the Sarmatian is concerned, there are no blooms, or increased frequencies, of dinoflagellate cysts that would benefit from such environmental conditions, like euryhaline Lingulodinium machaerophorum or protoperidinioids.The former species is common in low-salinity waters (e.g., [129]) frequently found in recent sediments of the Black and Caspian Seas [130].There are no freshwater algae, like Botryococcus and Pediastrum.On the contrary, samples from the Elphidium angulatum Zone yielded blooms of Prasinophyta Leiosphaera, which is known to occur in the Middle Badenian strata associated with hypersaline conditions.Moreover, sample 33 yielded the highest proportion of Polysphaeridium (Figure 9), a genus commonly associated with increased salinity [95].
Dinocyst degradation can be excluded, as the same samples yielded other aquatic palynomorphs.The co-occurrence of Elphidium in those samples can be explained by a larger (compared to samples for the palynological study) rock volume taken from the core, which could also include relatively thin, possibly bioturbated layers with benthic communities that appeared during short periods of better sea bottom ventilation.
The authors in [131] concluded that from fully marine to hypersaline conditions existed in the late Sarmatian, and our results suggest that this conclusion is also valid for the early Sarmatian.This conclusion is based on the foraminiferal and aquatic palynomorph records (Figure 11).Warm and humid climatic conditions indicated by pollen obviously are not in favour of hypersalinity.But this may be related to warm/cold current circulations (there is evidence of such changes in intervals where cold-water N. labyrinthus interlayers with warm-water Batiacasphaera).Moreover, hypersaline conditions could appear independent of climatic conditions, for example, in the cases of basin isolation, the temporary cessation of circulation, and the appearance of stratification.Spore-pollen assemblages record changes in vegetation on land and changes in marine salinity, which will not be evident in these assemblages unless they were caused by a very pronounced change in the climate.Ref. [132] recorded only a slight cooling, and a reduction in humidity was marked at 14-13.5 Ma.No clear change was observed there, only fluctuations with a slight trend, despite an important environmental change related to the mid-Badenian Salinity Crisis [23,133].The pollen record from marine sediments is not as precise as that from terrestrial/freshwater sediments, e.g., from lignite seams, which is something to be aware of.In the case of Babczyn, the spore-pollen assemblages are not very rich but are sufficient to draw some conclusions.Possible climatic fluctuations here could have been masked by changes in pollen transport and preservation conditions (i.e., water chemistry).Significant climate changes are not evident here though.

Conclusions
The qualitative and quantitative analyses of the foraminifera and the aquatic palynomorphs in the Badenian-Sarmatian strata of the Babczyn 2 borehole, one of the key sections in SE Poland, showed that the studied interval accumulated under variable, unstable sedimentary conditions in marine environments.
The dominance of infaunal benthic foraminifera species, mainly buliminids and uvigerinids, throughout the upper Badenian part of the studied interval (samples from 8 to 28) indicates mostly dysoxic and suboxic conditions.For the uppermost Badenian, mesotrophic conditions in surface waters and increased oxygenation of the bottom waters were observed.The Badenian/Sarmatian boundary, as correlated with a sudden extinction of stenohaline foraminifera, is placed just above sample 28 (within the lowermost part of the Syndesmya Beds).The overlying sample (29) is almost barren of foraminifera, and the lack of benthic forms may be explained by dysoxic conditions at the bottom of the sea.Euryhaline early Sarmatian benthic foraminiferal assemblages indicate a salinity increase, while the lack of planktonic foraminifera suggests a shallowing of the sea.
An acme of N. labyrinthus just below the Badenian/Sarmatian boundary may be the result of a temperature drop in sea-surface waters.The interval that occurred just above (samples 29 and 31) was characterised by a lack of dinoflagellate cysts and the flowering of Leiosphaeridiaceae, suggesting hypersaline conditions associated with stagnant, possibly stratified waters that led to anoxic conditions in the bottom waters, as evidenced by AOM.The subsequent cessation of these hypersaline conditions was caused by a possible sea-level rise and the gradual return of a less-saline water regime.The higher interval (samples  was deposited under more restricted and variable environmental condi-tions, including a brackish environment, as indicated by diverse fungal microremains found in the upper part of the profile.
The results of the spore-pollen analysis revealed the presence of mesophytic and wetland vegetation along shoreline of the Paratethys during sedimentation and indicated that the climate during the deposition of the sediments was generally warm temperate, mild, and rather humid.

Figure 4 .
Figure 4.The relative abundances (in percentages) of epifaunal, shallow infaunal, and infaunal taxa, the Shannon-Wiener indices H(S) and percentages of planktonic foraminifera in foraminiferal assemblages (P/B ratios); purple dashed line indicates the Badenian/Sarmatian boundary.

Figure 4 .
Figure 4.The relative abundances (in percentages) of epifaunal, shallow infaunal, and infaunal taxa, the Shannon-Wiener indices H(S) and percentages of planktonic foraminifera in foraminiferal assemblages (P/B ratios); purple dashed line indicates the Badenian/Sarmatian boundary.

Figure 7 .
Figure 7. Relative abundances of the most common benthic foraminiferal genera (in percentages) of the Babczyn 2 borehole; purple dashed line indicates the Badenian/Sarmatian boundary.

Figure 7 .
Figure 7. Relative abundances of the most common benthic foraminiferal genera (in percentages) of the Babczyn 2 borehole; purple dashed line indicates the Badenian/Sarmatian boundary.

Figure 11 .
Figure 11.Palaeoenvironmental changes in the late Badenian and early Sarmatian based on aquatic palynomorph and foraminiferal data from the Babczyn 2 borehole.

Figure 11 .
Figure 11.Palaeoenvironmental changes in the late Badenian and early Sarmatian based on aquatic palynomorph and foraminiferal data from the Babczyn 2 borehole.

Table 1 .
Distribution of aquatic palynomorphs in the upper Badenian of Babczyn 2 borehole (part 1).(*) indicates reworked taxa; their occurrence is not included in the total count.
(*) indicates reworked taxa; their occurrence is not included in the total count.

Table 3 .
Distribution of aquatic palynomorphs in the upper Badenian of Babczyn 2 borehole (part 2).(*) indicates reworked taxa; their occurrence is not included in the total count.

Table 4 .
Distribution of aquatic palynomorphs in the lower Sarmatian of Babczyn 2 borehole (part 2).(*) indicates reworked taxa; their occurrence is not included in the total count.