Paleomagnetic constraints on the chronology and geodynamics of the Dacian basin - eastern Paratethys

Reviewing previous studies and adding new paleomagnetic and micropaleontologic data, this paper focuses on the Middle Miocene chronology and stratigraphy in the Dacian Basin area -a critical moment in a critical location -a choking point between the water masses of the Eastern and Central Paratethys. Firstly, it gives a new time-frame for one major tectonic, biologic and basin evolution event -the intra-Sarmatian tectonic phase -that took place in the above mentioned time interval. Secondly, it proposes a revision of the timing for one of the regional sub-stage boundaries of the Middle Miocene in Paratethys (the Volhynian and the Bessarabian). And thirdly, it offers new, reliable magnetic data from four locations that will be further used in studies regarding tectonic rotations in the Carpathian orogenic system

The shutdown of an anoxic giant:Magnetostratigraphic dating of the end of the Maikop Sea

Paratethys, the lost sea of central Eurasia, was an anoxic giant during Oligocene – early Miocene (Maikop Series) times. With a size matching the modern-day Mediterranean Sea and a history of anoxic conditions that lasted for over 20 Myrs, the eastern part of this realm (Black Sea-Caspian Sea domain) holds key records for understanding the build-up, maintenance and collapse of anoxia in marginal seas. Here, we show that the collapse of anoxic Maikop conditions was caused by middle Miocene paleogeographic changes in the Paratethys gateway configuration, when a mid-Langhian (Badenian-Tarkhanian) transgression flooded and oxygenated the Eastern Paratethys. We present an integrated magneto-biostratigraphic framework for the early Middle Miocene (Tarkhanian-Chokrakian-Karaganian regional stages) of the Eastern Paratethys and date the lithological transition from anoxic black shales of the Maikop Series to fossiliferous marine marls and limestones of the regional Tarkhanian stage. For this purpose, we selected two long and time-equivalent sedimentary successions, exposed along the Belaya and the Pshekha rivers, in the Maikop type area in Ciscaucasia (southern Russia). We show that a significant but short marine incursion took place during the Tarkhanian, ending the long-lasting Maikop anoxia of the basin. Our magnetostratigraphic results reveal coherent polarity patterns, which allow a straightforward correlation with the time interval 15–12 Ma of the Geomagnetic Polarity Time Scale. The Tarkhanian flooding occurred during a relatively short normal polarity interval that correlates with C5Bn, resulting in an age of 14.85 Ma. The regional Tarkhanian/Chokrakian stage boundary is located within C5ADn at an age of 14.75 Ma and the Chokrakian/Karaganian boundary is tentatively correlated with C5ACn and an age of 13.9–13.8 Ma. Our new Tarkhanian flooding age reveals a paleogeographic scenario that is different from many previous reconstructions. Instead of envisaging marine connections to the Indian Ocean, we show that major changes in connectivity between the Eastern and Central Paratethys seas have caused the influx of marine waters during the Tarkhanian. An increase in marine connectivity with the Mediterranean during a short episode of rapid sea-level rise triggered mixing and ended the widespread anoxia in the Eastern Paratethys. The mixing episode was short-lived (~100 kyr) as the sea-level rise slowed down and connectivity degraded because of tectonic uplift in the gateway area

A Late Maeotian age (6.7–6.3 Ma) for the enigmatic “Pebbly Breccia” unit in DSDP Hole 380A of the Black Sea

Various hypotheses exist on the age and origin of the so-called “Pebbly Breccia” unit in the deep-sea record of DSDP Hole 380A of the Euxinian (Black Sea) Basin. Here, we present a detailed study of diatom and nannofossil assemblages of Hole 380A. Our diatom records show a characteristic sequence of appearance of markers species, which we can correlate to the recently established bio-magnetostratigraphic time frame of the Zheleznyi Rog section on the Black Sea coast of the Taman Peninsula (Russia). It shows that the Pebbly Breccia is sandwiched between Upper Maeotian deposits, and must have been deposited at an age between 6.7 and 6.3 Ma. The appearance of nannoplankton and the marine diatom association at above the Pebbly breccia (Unit IVc) suggests a short-term incursion of marine conditions. The age of Unit IVc, based on diatom data, is 6.3–6.1 Ma. The nannoplankton record is mainly represented by species that do not have stratigraphic value. The previously reported presence of Ceratolithus acutus in the Black Sea is explained by misinterpretation of destructed elements of ascidian spicules. We conclude that the Pebbly Breccia is not related to a desiccated Black Sea at Messinian Salinity Crisis times, but it corresponds to a late Maeotian episode of gravitational instability in the SW Black Sea region

A Late Maeotian age (6.7–6.3 Ma) for the enigmatic “Pebbly Breccia” unit in DSDP Hole 380A of the Black Sea

Various hypotheses exist on the age and origin of the so-called “Pebbly Breccia” unit in the deep-sea record of DSDP Hole 380A of the Euxinian (Black Sea) Basin. Here, we present a detailed study of diatom and nannofossil assemblages of Hole 380A. Our diatom records show a characteristic sequence of appearance of markers species, which we can correlate to the recently established bio-magnetostratigraphic time frame of the Zheleznyi Rog section on the Black Sea coast of the Taman Peninsula (Russia). It shows that the Pebbly Breccia is sandwiched between Upper Maeotian deposits, and must have been deposited at an age between 6.7 and 6.3 Ma. The appearance of nannoplankton and the marine diatom association at above the Pebbly breccia (Unit IVc) suggests a short-term incursion of marine conditions. The age of Unit IVc, based on diatom data, is 6.3–6.1 Ma. The nannoplankton record is mainly represented by species that do not have stratigraphic value. The previously reported presence of Ceratolithus acutus in the Black Sea is explained by misinterpretation of destructed elements of ascidian spicules. We conclude that the Pebbly Breccia is not related to a desiccated Black Sea at Messinian Salinity Crisis times, but it corresponds to a late Maeotian episode of gravitational instability in the SW Black Sea region

A Late Maeotian age (6.7–6.3 Ma) for the enigmatic “Pebbly Breccia” unit in DSDP Hole 380A of the Black Sea

Various hypotheses exist on the age and origin of the so-called “Pebbly Breccia” unit in the deep-sea record of DSDP Hole 380A of the Euxinian (Black Sea) Basin. Here, we present a detailed study of diatom and nannofossil assemblages of Hole 380A. Our diatom records show a characteristic sequence of appearance of markers species, which we can correlate to the recently established bio-magnetostratigraphic time frame of the Zheleznyi Rog section on the Black Sea coast of the Taman Peninsula (Russia). It shows that the Pebbly Breccia is sandwiched between Upper Maeotian deposits, and must have been deposited at an age between 6.7 and 6.3 Ma. The appearance of nannoplankton and the marine diatom association at above the Pebbly breccia (Unit IVc) suggests a short-term incursion of marine conditions. The age of Unit IVc, based on diatom data, is 6.3–6.1 Ma. The nannoplankton record is mainly represented by species that do not have stratigraphic value. The previously reported presence of Ceratolithus acutus in the Black Sea is explained by misinterpretation of destructed elements of ascidian spicules. We conclude that the Pebbly Breccia is not related to a desiccated Black Sea at Messinian Salinity Crisis times, but it corresponds to a late Maeotian episode of gravitational instability in the SW Black Sea region

Litho- and biostratigraphic data of lower-middle Miocene sections in the Transylvanian basin and SE Carpathian Foredeep (Romania)

Litho- and biostratigraphic data are provided of 5 stratigraphic sections in Romania covering the “Badenian” marine flooding that occurred in the Central Paratethys during the middle Miocene (Langhian). The dataset includes stratigraphic logs and descriptions of the profiles, and biostratigraphic analyses on calcareous nannofossils and foraminifera. In addition, characteristic stratigraphic features and representative fossils, including tiny Streptochilus foraminifera in the Campiniţa section in the SE Carpathian Foredeep, are presented in photographs. The data show that the flooding is characterized by the sudden abundance of Langhian calcareous nannofossils and foraminifera with a strong Mediterranean affinity

Litho- and biostratigraphic data of lower-middle Miocene sections in the Transylvanian basin and SE Carpathian Foredeep (Romania)

Litho- and biostratigraphic data are provided of 5 stratigraphic sections in Romania covering the “Badenian” marine flooding that occurred in the Central Paratethys during the middle Miocene (Langhian). The dataset includes stratigraphic logs and descriptions of the profiles, and biostratigraphic analyses on calcareous nannofossils and foraminifera. In addition, characteristic stratigraphic features and representative fossils, including tiny Streptochilus foraminifera in the Campiniţa section in the SE Carpathian Foredeep, are presented in photographs. The data show that the flooding is characterized by the sudden abundance of Langhian calcareous nannofossils and foraminifera with a strong Mediterranean affinity

Litho- and biostratigraphic data of lower-middle Miocene sections in the Transylvanian basin and SE Carpathian Foredeep (Romania)

Litho- and biostratigraphic data are provided of 5 stratigraphic sections in Romania covering the “Badenian” marine flooding that occurred in the Central Paratethys during the middle Miocene (Langhian). The dataset includes stratigraphic logs and descriptions of the profiles, and biostratigraphic analyses on calcareous nannofossils and foraminifera. In addition, characteristic stratigraphic features and representative fossils, including tiny Streptochilus foraminifera in the Campiniţa section in the SE Carpathian Foredeep, are presented in photographs. The data show that the flooding is characterized by the sudden abundance of Langhian calcareous nannofossils and foraminifera with a strong Mediterranean affinity

Litho- and biostratigraphic data of lower-middle Miocene sections in the Transylvanian basin and SE Carpathian Foredeep (Romania)

Litho- and biostratigraphic data are provided of 5 stratigraphic sections in Romania covering the “Badenian” marine flooding that occurred in the Central Paratethys during the middle Miocene (Langhian). The dataset includes stratigraphic logs and descriptions of the profiles, and biostratigraphic analyses on calcareous nannofossils and foraminifera. In addition, characteristic stratigraphic features and representative fossils, including tiny Streptochilus foraminifera in the Campiniţa section in the SE Carpathian Foredeep, are presented in photographs. The data show that the flooding is characterized by the sudden abundance of Langhian calcareous nannofossils and foraminifera with a strong Mediterranean affinity

The mid-Langhian flooding in the eastern Central Paratethys: integrated stratigraphic data from the Transylvanian Basin and SE Carpathian Foredeep

The mid-Langhian (“Badenian”) flooding fully reconnected the semi-isolated Central Paratethys realm with the Mediterranean and, thereby, drastically changed the middle Miocene paleogeography of Central Europe. Due to the scattered stratigraphic record and scarcity of independent age constraints in some areas, the precise age and underlying mechanism are still debated. We present integrated chronostratigraphic data from five sections in the eastern part of the system to reconstruct the flooding event distal from the strait to the Mediterranean. By applying modern Mediterranean biochronology (planktonic foraminifera and calcareous nannofossils), supplemented by an 40Ar/39Ar age on a tuff, we demonstrate that the widespread open marine settings in the NW Transylvanian Basin were definitely installed after 14.9 Ma (MMi4d biozone), and in most areas before 14.4 Ma. In the marginal study area in the SE Carpathian Foredeep, fully marine conditions likely set in slightly later (14.6–14.4 Ma). There, short-lived marine incursions into the brackish environment occurred since the latest Burdigalian (“pre-flooding phase”). The new ages overlap with the flooding in the majority of the Central Paratethys (~ 14.9–14.4 Ma), and with marine overflow into the Black Sea (14.85 Ma). We suggest that the transgression was driven by subsidence of the Pannonian Basin, by creating accommodation space and diminishing barriers between sub-basins, but was likely enhanced by a global sea-level rise. Finally, we speculate that the scarcity of all calcareous material in the SE Carpathian Foredeep before the mid-Langhian flooding might be related to pulses of nutrient-rich brackish and low pH water from the neighboring Black Sea Basin