Taxonomy and palaeoecology of continental Gastropoda (Mollusca) from the Late Pleistocene mammoth-bearing site of Bullendorf in NE Austria

We present a taxonomic and palaeoecological analysis of a continental mollusc fauna from a mammoth-bearing succession near Bullendorf in Lower Austria. The taxonomic analysis comprises morphological descriptions and SEM documentation of 15 Pleistocene gastropod species. A Principal Component Analysis of the quantitative and qualitative composition of the investigated samples reveals a stratigraphic succession of four mollusc assemblages defined herein as Galba truncatula assemblage, Succinella oblonga assemblage, Pupilla muscorum/loessica and Pupilla alpicola/sterrii assemblages. The autecological requirements of the species of each assemblage allow a reconstruction of the palaeoenvironmental history of the section with alternating dry and humid conditions within a general cooling trend. Despite generally low mollusc density and species richness, the Bullendorf site allows important insight into latest Quaternary regional environmental conditions and climate. Based on the comparison with similar mollusc sites across Europe, a biostratigraphic correlation with the Late Pleistocene (~110\u201312 ka) is propose

New paleoenvironmental insights on the Miocene condensed phosphatic layer of Salento (southern Italy) unlocked by the coral-mollusc fossil archive

From the Late Oligocene to the Late Miocene, the central Mediterranean area was characterized by the extensive deposition of phosphate-rich sediments. They are usually represented by 10 to 20-cm-thick hardgrounds made of phosphatic and glauconitic sediments containing a rich macrofossil association. This study represents the first thorough investigation of the biotic assemblage of Mediterranean phosphorites aimed at collecting new information on the environmental factors controlling their deposition. The Serravallian/Tortonian phosphatic deposits of the Salento Peninsula (“Aturia level”) have been selected for the abundance of fossil remains and special attention is given to the coral–mollusc association. Two different facies have been recognized: a basal coral rudstone that includes most of the macrofossils, superimposed by a detrital rudstone made of thin layers mainly composed of phosphatic fragments. These two facies are separated by a phosphatic crust several millimeters in thickness. The coral assemblage contains at least 17 azooxanthellate taxa belonging to four families, while the molluscs are represented by a rich gastropod fauna (26 species), associated with bivalves (18 species) and cephalopods (two species). Four distinct depositional phases have been recognized, with the coral rudstone representing the key-facies to reconstruct the onset of the “Aturia level” and the original environment of its fossil content. The composition of the coral–mollusc association has been reliably compared with present-day analog taxa, suggesting the occurrence of a heterogeneous seafloor formed by rocky substrates and accumulations of soft sediment, at around 100–350-m water depth, and under the influence of moderate-to-strong bottom currents rich in nutrients and resuspended organic matter

Evolution, turnovers and spatial variation of the gastropod fauna of the late Miocene biodiversity hotspot Lake Pannon

AbstractLake Pannon constituted the biggest hotspot of biodiversity in the late Cenozoic of Europe, comprising a total diversity of almost 600 gastropod species. The gastropod fauna of this huge brackish system, which existed over about seven million years from the late Miocene to earliest Pliocene within the Pannonian Basin System, has been well documented by a great many of taxonomic works. In contrast, the faunal development within the lake has not been properly addressed from a statistical point of view. The present investigation demonstrates that species were not homogeneously distributed across space and time, generating uneven and temporally shifting patterns of species richness and degree of point endemism across the lake. The faunal compositions of the time intervals analyzed were highly different, contrasting simple species accumulation as suggested by the overall numbers. Shifting patterns of local diversity within the lake reflect changing paleo-shorelines, resulting from prograding river systems entering and successively diminishing the lake surface area. As mainly herbivorous grazers and predominantly shallow-water inhabitants, the gastropods traced the moving shelf margins and vegetation belts accordingly, producing the observed diversity shifts. In addition, each time interval is characterized by a high degree of provincialism, which is considered to reflect high habitat diversity. This claim is supported by the complex subaqueous topography and the presence of extensive delta plains produced by the incoming river systems. A potential driver for provincialism might be the adaptation of species to distinct water depths (and related parameters). Finally, the notable differences among the faunal compositions of the upper Pannonian strata and the succeeding lower Viviparus beds, especially regarding family-level, indicate an environmental turnover at the transition. Brackish-water species are mostly replaced by typical freshwater elements, indicating strong fluvial influence. Based on our results and latest stratigraphic data, we conclude that the Viviparus beds were deposited in a different environment, replacing Lake Pannon in the southern Pannonian Basin in the early Pliocene

IN SEARCH OF THE EGGENBURGIAN – OTTNANGIAN BOUNDARY AT THE SOUTHEASTERN MARGIN OF THE BOHEMIAN MASSIF (LOWER AUSTRIA)

At the south-eastern margin of the Bohemian Massif in Lower Austria Eggenburgian to Ottnangian sediments are widespread. In the wider surroundings of Eggenburg nearshore clastic deposits of the upper Eggenburgian (Kühnring Mb., Burgschleinitz Fm., Gauderndorf Fm.) occur, which are discordantly overlain by shallow marine sublittoral bioclastic limestone of the Zogelsdorf Fm. Due to the ongoing transgression the Zogelsdorf Fm. shows a fining and deepening upward succession, passing upsection and laterally into marine clays and marls of the Zellerndorf Fm.Two completely cored logs from Limberg and Pulkau show this sedimentary succession above the crystalline basement. As in many outcrops, in the well Limberg KB2 on top of the Burgschleinitz Fm. a transgressional conglomerate occurs at the base of typical Zogelsdorf Fm. followed by pelites of the Zellerndorf Fm. The well Pulkau S1 exhibits between clastics of the Burgschleinitz Fm. and sands and limestone of the Zogelsdorf-Fm. a 4.5 m pelitic sequence with two tuffitic horizons. Between those notdateable tuffitic clays, badly sorted gravelly and sandy clay with molluscs like Granulolabium plicatum, Ostrea digitalina, Perna aquitanica, Cerastoderma edule, Taras rotundatus, Tellina planata, Cordiopsis incrassatus, Turritella sp., and Natica sp. indicates a deepening upward lagoonal environment. In dark gray fine bedded silty clays above thin shelled bivalves (Cardiidae, Veneridae, Lucinidea) and gastropods (Turritella eryna, Granulolabium plicatum) also point to shallow marine lagoonal conditions. This pelitic sequence is concordantly overlain by sands and sandy limestone of the Zogelsdorf Fm. and silty clay of the Zellerndorf Fm.Calcareous nannoplankton associations from the Burgschleinitz Fm. in Limberg KB2 can be correlated by Triquatrorhabdulus carinatus and Helicosphaera ampliaperta with the upper part of NN2. Sediments from the Zogelsdorf Fm. in the lower part of Limberg KB2 can be assigned to NN2/NN3 by H. ampliaperta and T. carinatus. Assemblages with H. ampliaperta and Reticulofenestra excavata in the lowermost part of the Zellerndorf Fm. in Pulkau S1 point to NN3.The successions in both wells show at the base upper Eggenburgian marine deposit (Burgschleinitz Fm.) followed by a regressional phase and a renewed transgression initiating the deposition in lagoonal facies in Pulkau S1. This regression presumably correlates with the main regional hiatus at the base of the Zogelsdorf Fm. and can be consequently correlated with the 3rd Order Sequence Stratigraphic Boundary Bur 3

Revised Middle Miocene datum for initial marine fl ooding of North Croatian Basins (Pannonian Basin System, Central Paratethys)

The Pannonian Basin System (PBS) originated during the Early Miocene as a result of extensional processes between the Alpine-Carpathian and the Dinaride Orogenic Belts. The Paratethys Sea flooded the new basins successively during the Karpatian (late Burdigalian, Early Miocene) and the Early Badenian (middle Langhian, Middle Miocene). The North Croatian Basins (NCB) occupied the south-western margin of the PBS and the Central Paratethys Sea. Their initial marine flooding has until now been dated as Karpatian in age. The transgression into the NCB invaded a lacustrine environment, representing the northern prolongation of the vast Dinaride Lake System extending southwards as far as the Adriatic Plate. We reinvestigate two sections from opposite margins of the NBS – from Mt. Medvednica in the west and from Mt. Požeška in the east, including the corresponding lowermost marine Miocene deposits, in order to critically examine the Karpatian datum. Our new biostratigraphic data, integrating calcareous nannoplankton, planktic and benthic foraminifera, diatom and mollusc records, have substantially revised the previous interpretation. The presence of a calcareous nannoplankton assemblage of the NN5 Zone and the planktic and benthic foraminifera of the regional Lower Lagenidae Zone now place the transgression into the main Early Badenian transgressive pulse of Central Paratethys. Consequently, the initial marine transgression correlates accurately with the middle part of the Early Badenian, which is more than 2 m.y. younger than the previously inferred datum, and at least 1 m.y. younger than the lower boundary of the Badenian and the Middle Miocene, respectively. Finally, the basal lacustrine infill of the NCB, previously dated as Ottnangian (middle Burdigalian, Early Miocene) and continuously grading into marine deposits, has also to be reconsidered as Early Badenian

Stratigraphic and paleogeographic significance of lacustrine mollusks from the Pliocene Viviparus beds in central Croatia

The mollusk fauna from the Pliocene Viviparus beds of Vukomeričke Gorice hills in central Croatia was investigated at four sites in the region of Kravarsko, S of Zagreb. The region represents a Pleistocene dome-anticline at the southern margin of the Sava depression. Sediments are dominated by clay, bearing some sand, gravel and lignite intercalations. The mollusks, comprising 11 gastropod and 2 bivalve species, prove the studied deposits to derive from the long-lived, highly endemic Lake Slavonia. The taxonomic revisions include the introductions of Viviparus kochanskyae n. sp. for specimens from Lake Slavonia previously identified with V. fuchsi NEUMAYR, 1872 and Prososthenia? praeslavonica n. nom. replacing the primary homonym Hydrobia vitrella BRUSINA, 1897 non Stefanescu, 1896. Recognized as an independent phase in the geodynamic evolution of the Pannonian Basin, the new regional stage Cernikian is introduced for the succession, defined by the complete depositional sequence of the Viviparus beds. Two stratigraphic horizons detected in the studied sites are constrained by the Lower Cernikian Viviparus kochanskyae and the Upper Cernikian Viviparus hoernesi zones and stay in perfect agreement with previous regional data. Timing of the Lake Slavonia history is enabled through several zonal markers calibrated to the Geological Time Scale in the Dacian Basin. Accordingly, the Lower Cernikian transgression dates to c. 4.3 Ma, the Upper Cernikian to c. 3.1 Ma, indicating strong alteration of the lacustrine depositional settings during the Pliocene, most likely related to changes in the regional climate. Interestingly, the second transgression of Lake Slavonia is marked by the evolution of strongly sculptured viviparid shells and coincides with the Pliocene Climate Optimum.</p

The Sarmatian/Pannonian boundary at the western margin of the Vienna Basin (City of Vienna, Austria)

Abstract Sarmatian and Pannonian cores, drilled at the western margin of the Vienna Basin in the City of Vienna, reveal a complex succession of marine and lacustrine depositional environments during the middle to late Miocene transition. Two Sarmatian and two Pannonian transgressive-regressive sequences were studied in detail. Identical successions of benthic faunal assemblages and similar patterns in magnetic susceptibility logs characterise these sequences. This allows a correlation of the boreholes over a distance of ~3.5 km across one of the major marginal faults of the Vienna Basin. Biostratigraphic data, combined with rough estimates of sedimentation rates, reveal large gaps between these sequences, suggesting that only major transgressions reached this marginal area. In particular, during the Sarmatian-Pannonian transition, the basin margin completely emerged and turned into a terrestrial setting for at least 600 ka

Timing, cause and impact of the late Eocene stepwise sea retreat from the Tarim Basin (west China)

International audienceA vast shallow epicontinental sea extended across Eurasia and was well-connected to the Western Tethys before it retreated westward and became isolated as the Paratethys Sea. However, the palaeogeography and the timing of this westward retreat are too poorly constrained to determine potential wider environmental impacts, let alone understanding underlying mechanisms of the retreat such as global eustasy and tectonism associated with the Indo-Asia collision. Here, an improved chronostratigraphic and palaeogeographic framework is provided for the onset of the proto-Paratethys Sea retreat at its easternmost extent in the Tarim Basin in western China is provided. Five different third-order sea-level cycles can be recognised from the Cretaceous-Palaeogene sedimentary record in the Tarim Basin, of which the last two stepped successively westwards as the sea retreated after the maximum third incursion. New biostratigraphic data from the fourth and fifth incursions at the westernmost margin of the Tarim Basin are compared to our recent integrated bio-magneto-stratigraphic results on the fourth incursion near the palaeodepocentre in the south-western part of the basin. While the fourth incursion extended throughout the basin and retreated at ~ 41 Ma (base C18r), the last and fifth incursion is restricted to the westernmost margin and its marine deposits are assigned a latest Bartonian-early Priabonian age from ~ 38.0 to ~ 36.7 Ma (near top C17n.2n to base C16n.2n). Similar to the fourth, the fossil assemblages of the fifth incursion are indicative of shallow marine, near-shore conditions and their widespread distribution across Eurasia suggests that the marine connection to the Western Tethys was maintained. The lack of diachronicity of the fourth incursion between the studied sections across the southwest Tarim Basin suggests that the sea entered and withdrew relatively rapidly, as can be expected in the case of eustatic control on a shallow epicontinental basin. However, the westward palaeogeographic step between the fourth and fifth incursions separated by several millions of years rather suggests the combined long-term effect of tectonism, possibly associated with early uplift of the Pamir-Kunlun Shan thrust belt. The fourth and fifth regressions are time-equivalent with significant aridification steps recorded in the Asian interior, thus supporting climate modelling results showing that the stepwise sea retreat from Central Asia amplified the aridification of the Asian interior