Eva Halásová

The Brodno section — a potential regional stratotype of the Jurassic/Cretaceous boundary (Western Carpathians)

The Brodno section — a potential regional stratotype of the Jurassic/Cretaceous boundary (Western Carpathians) Compared to coeval successions from the Carpathians, the continuous Jurassic-Cretaceous (J/K) pelagic limestone succession of the Brodno section offers the best possibility to document the J/K passage in a wide area. This section comprises a complete calpionellid, and nannofossil stratigraphic record, that supports the older paleomagnetic data. Moreover, the sequence stratigraphy and stable isotope (δ18O, δ13C) data gave important results, too, enabling comparison with known key sections from the Mediterranean Tethys area.

High resolution stratigraphy of the Jurassic-Cretaceous boundary interval in the Gresten Klippenbelt (Austria)

High resolution stratigraphy of the Jurassic-Cretaceous boundary interval in the Gresten Klippenbelt (Austria) The key objective of investigation of hemipelagic sediments from the Gresten Klippenbelt (Blassenstein Formation, Ultrahelvetic paleogeographic realm) was to shed light on environmental changes around the Jurassic-Cretaceous (J/K) boundary on the northern margin of the Penninic Ocean. This boundary is well exposed in a newly discovered site at Nutzhof. Around the critical interval including the boundary, this new outcrop bears a rich microplanktonic assemblage characterized by typical J/K (Tithonian/Berriasian) boundary faunas. The Nutzhof section is located in the Gresten Klippenbelt (Lower Austria) tectonically wedged into the deep-water sediments of the Rhenodanubian Flysch Zone. In Late Jurassic-Early Cretaceous time the Penninic Ocean was a side tract of the proto-North Atlantic Oceanic System, intercalated between the European and the Austroalpine plates. Its opening started during the Early Jurassic, induced by sea floor spreading, followed by Jurassic-Early Cretaceous deepening of the depositional area of the Gresten Klippenbelt. These tectonically induced paleogeographic changes are mirrored in the lithology and microfauna that record a deepening of the depositional environment from Tithonian to Berriasian sediments of the Blassenstein Formation at Nutzhof. The main lithological change is observed in the Upper Tithonian Crassicollaria Zone, in Chron M20N, whereas the J/K boundary can be precisely fixed at the Crassicollaria-Calpionella boundary, within Chron M19n.2n. The lithological turnover of the deposition from more siliciclastic pelagic marl-limestone cycles into deep-water pelagic limestones is correlated with the deepening of the southern edge of the European continent at this time. Within the Gresten Klippenbelt Unit, this transition is reflected by the lithostratigraphic boundary between siliciclastic-bearing marl-limestone sedimentation in the uppermost Jurassic and lowermost Cretaceous limestone formation, both within the Blassenstein Formation. The cephalopod fauna (ammonites, belemnites, aptychi) and crinoids from the Blassenstein Formation, correlated with calcareous microfossil and nannofossil data combined with isotope and paleomagnetic data, indicate the Tithonian to middle Berriasian (Hybonoticeras hybonotum Zone up to the Subthurmannia occitanica Zone; M17r-M21r). The succession of the Nutzhof section thus represents deposition of a duration of approximately 7 Myr (ca. 150-143 Ma). The deposition of the limestone, marly limestone and marls in this interval occurred during tectonically unstable conditions reflected by common allodapic material. Along with the integrated biostratigraphic, geochemical and isotopic analysis, the susceptibility and gamma-ray measurements were powerful stratigraphic tools and important for the interpretation of the paleogeographic setting. Two reverse magneto-subzones, Kysuca and Brodno, were detected within magnetozones M20n and M19n, respectively.

An account of the bio- and magnetostratigraphy of the Upper Tithonian—Lower Berriasian interval at Le Chouet, Drôme (SE France)

Abstract This paper discusses the results of a study of the Le Chouet section, its lithologies, facies, magnetic properties and fossil record (ammonites, calcareous nannofossils, calpionellids and calcareous dinoflagellates). Data obtained have been applied to give a precise biostratigraphy for this carbonate sequence as well as a paleoenvironmental reconstruction. Its relationship to magnetostratigraphy, based on a modern study of a French site, is important. Investigation of the micro- and macrofossils shows that the site comprises a sedimentary sequence in the Microcanthum to Jacobi ammonite Zones, and the Chitinoidella, Crassicollaria and Calpionella Zones. Several calpionellid and nannofossil bioevents have been recorded on the basis of the distribution of stratigraphically important planktonic organisms. The site allows us to calibrate the levels of various biomarkers and biozonal boundaries, and correlate them with the magnetozones M20n, M19r and M19n.

Biostratigraphy, sedimentology and paleoenvironments of the northern Danube Basin: Ratkovce 1 well case study

Abstract The Ratkovce 1 well, drilled in the Blatné depocenter of the northern Danube Basin penetrated the Miocene sedimentary record with a total thickness of 2000 m. Biostratigraphically, the NN4, NN5 and NN6 Zones of calcareous nannoplankton were documented; CPN7 and CPN8 foraminifer Zones (N9, 10, 11 of the global foraminiferal zonation; and MMi4a; MMi5 and MMi6 of the Mediterranean foraminiferal zonation were recognized. Sedimentology was based on description of well core material, and together with SP and RT logs, used to characterize paleoenvironmental conditions of the deposition. Five sedimentary facies were reconstructed: (1) fan-delta to onshore environment which developed during the Lower Badenian; (2) followed by the Lower Badenian proximal slope gravity currents sediments; (3) distal slope turbidites were deposited in the Lower and Upper Badenian; (4) at the very end of the Upper Badenian and during the Sarmatian a coastal plain of normal marine to brackish environment developed; (5) sedimentation finished with the Pannonian-Pliocene shallow lacustrine to alluvial plain deposits. The provenance analysis records that the sediment of the well-cores was derived from crystalline basement granitoides and gneisses and from the Permian to Lower Cretaceous sedimentary cover and nappe units of the Western Carpathians and the Eastern Alps. Moreover, the Lower Badenian volcanism was an important source of sediments in the lower part of the sequence.

Brachiopods and bryozoans from the Sandberg section (ViennaBasin, Central Paratethys) and their significance forenvironmental interpretation of the Early Sarmatian (= MiddleMiocene) Sea.

Brachiopods and bryozoans are described for the first time from the upper part of the Sandberg section (Vienna Basin, Central Paratethys, Slovakia) dated by foraminifers and calcareous nannoplankton as Early Sarmatian (= Late Serravallian). Three brachiopod species, i.e. Gryphus miocenicus (Michelotti, 1847), Argyrotheca cuneata (Risso, 1826) and Joania cordata (Risso, 1826), have been identified. Bryozoans are represented by at least 11 species, i.e. Umbonula macrocheila (Reuss, 1847), Margaretta cereoides (Ellis et Solander, 1786), Plagioecia rotula (Reuss, 1847), Schizoporella dunkeri (Reuss, 1847), Calpensia gracilis (Munster, 1826), Escharella tenera (Reuss, 1874), Mollia cf. patellaria (Moll, 1803), Vibracella trapezoidea (Reuss, 1847), Smittina cervicornis (Pallas, 1766), Porella sp., and an unidentified calloporid. Despite the fact that brackish conditions are commonly expected in the Vienna Basin during this period, the assemblage indicates full marine (stenohaline) conditions.

Sepia from the Miocene of the Central Paratethys: new taxa and notes on late Cenozoic cuttlefish diversity

A new and locally abundant species of Sepia, S. juliebarborarum sp. nov., and single records of S. aff. loerentheyi and S. aff. sanctacrucensis from the upper Badenian of Slovakia and Austria, S. mikuzi sp. nov., S. aff. mikuzi sp. nov. and Sepia sp. from the middle Badenian of Slovenia, document a greater Miocene sepiid diversity in the Central Paratethys than previously recorded. In the present study, Miocene sepiids from the Central Paratethys are systematically revised and, in part, compared to other coeval taxa from elsewhere. Middle Miocene diversity in the Central Paratethys amounts to nine species, inclusive of four taxa retained in open nomenclature. Here we use the morphology of the dorsal shield and septal suture lines as key features for systematic assignment at the species level. Usage of the generic name Sepia for these Miocene sepiids is corroborated by uniquely preserved material of S. vindobonensis from the middle Badenian of Austria. This reveals only minor morphological differences during ontogeny from the Recent type species of Sepia, S. officinalis. The stratigraphical range of sepiids in the Central Paratethys is reinterpreted and shown to be early to late Badenian. Miocene Sepia diversity in the Central Paratethys is greater than previously supposed, which supports normal marine conditions and an open connection with the Mediterranean. http://zoobank.org/urn:lsid:zoobank.org:pub:3B32BA47-EB28-4A75-95FE-6349C08BB5EA.

Integrated biostratigraphical, sedimentological and provenance analyses with implications for lithostratigraphic ranking: the Miocene Komjatice depression of the Danube Basin

Abstract The Komjatice depression, situated on the Danube Basin’s northern margin, represents a sub-basin of the Neogene epicontinental Central Paratethys Sea and Lake Pannon. The paper provides an insight into the character of sediment provenance evolution by study of well cores (ZM-1, IV-1, MOJ-1, VR-1 wells). A modern combination of provenance, sedimentology and biostratigraphy together with the reported redefinition of Pannonian formations resulted in a new lithostratigraphy of the study area. Moreover, newly published volcanic rock age data were used for calibration of biostratigraphy. The overall age span of the sedimentary fill is occupied only by late Badenian–Sarmatian (Serravallian) to Pannonian (Tortonian–Messinian) strata: 1) the basal alluvial sediments of the newly defined Zlaté Moravce Formation; 2) late Badenian–Sarmatian (Serravalian) marine sediments of the Vráble-Pozba Fm., connected with tectonic opening of the depression; 3) Pannonian (Tortonian) coarse grained sediments of the Nemčiňany Fm. with an erosional base; 4) Pannonian (Tortonian–Messinian) predominantly fine-grained, basin floor to slope Ivanka Fm., sandy deltaic Beladice Fm. and predominantly muddy, alluvial Volkovce Fm. In the middle Miocene provenance is situated in Paleozoic sequences and Neogene volcanic rocks occurring currently in the NE. During the late Miocene, provenance is changed to the NNW (Tribeč Mts.), although the transport from the NE also remained.

Towards better correlation of the Central Paratethys regional time scale with the standard geological time scale of the Miocene Epoch

Abstract Depositional sequences originating in semi-enclosed basins with endemic biota, partly or completely isolated from the open ocean, frequently do not allow biostratigraphic correlations with the standard geological time scale (GTS). The Miocene stages of the Central Paratethys represent regional chronostratigraphic units that were defined in type sections mostly on the basis of biostratigraphic criteria. The lack of accurate dating makes correlation within and between basins of this area and at global scales difficult. Although new geochronological estimates increasingly constrain the age of stage boundaries in the Paratethys, such estimates can be misleading if they do not account for diachronous boundaries between lithostratigraphic formations and for forward smearing of first appearances of index species (Signor-Lipps effect), and if they are extrapolated to whole basins. Here, we argue that (1) geochronological estimates of stage boundaries need to be based on sections with high completeness and high sediment accumulation rates, and (2) that the boundaries should preferentially correspond to conditions with sufficient marine connectivity between the Paratethys and the open ocean. The differences between the timing of origination of a given species in the source area and timing of its immigration to the Paratethys basins should be minimized during such intervals. Here, we draw attention to the definition of the Central Paratethys regional time scale, its modifications, and its present-day validity. We suggest that the regional time scale should be adjusted so that stage boundaries reflect local and regional geodynamic processes as well as the opening and closing of marine gateways. The role of eustatic sea level changes and geodynamic processes in determining the gateway formation needs to be rigorously evaluated with geochronological data and spatially-explicit biostratigraphic data so that their effects can be disentangled.