The end of the Great Khersonian Drying of Eurasia: Magnetostratigraphic dating of the Maeotian transgression in the Eastern Paratethys

Abstract

Central Eurasia underwent significant palaeoclimatic and palaeogeographic transformations during the middle to late Miocene. The open marine ecosystems of the Langhian and Serravallian seas progressively collapsed and were replaced in the Tortonian by large endorheic lakes. These lakes experienced major fluctuations in water level, directly reflecting the palaeoclimatic conditions of the region. An extreme lowstand of the Eastern Paratethys lake (−300 m) during the regional Khersonian stage reveals a period of intensely dry conditions in Central Eurasia causing a fragmentation of the Paratethys region. This period of “Great Drying” ended by a climate change towards more humid conditions at the base of the Maeotian stage, resulting in a large transgressive event that reconnected most of the Paratethyan basins. The absence of a robust time frame for the Khersonian–Maeotian interval hampers a direct correlation with the global records and complicates a thorough understanding of the underlying mechanisms. Here we present a new chronostratigraphic framework for the Khersonian and Maeotian deposits of the Dacian Basin of Romania, based on integrated magneto‐biostratigraphic studies on long and continuous sedimentary successions. We show the dry climate conditions in the Khersonian start at 8.6–8.4 Ma. The Khersonian/Maeotian transition is dated at 7.65–7.5 Ma, several million years younger than previous estimates. The Maeotian transgression occurs later (7.5–7.4 Ma) in more marginal and shallower basins, in agreement with the time transgressive character of the flooding. In addition, we date a sudden water level drop of the Eastern Paratethys lake, the Intra‐Maeotian Event (IME), at 6.9 Ma, and hypothesize that this corresponds to a reconnection phase with the Aegean basin of the Mediterranean. Finally, we discuss the potential mechanisms explaining the particularities of the Maeotian transgression and conclude that the low salinity and the seemingly “marine influxes” most likely correspond to episodes of intrabasinal mixing in a gradual and pulsating transgressive setting.

Report of Geophysical Center of RAS for 2018: Results of the State Task

“…лет соответственно. В то же время, согласно представлениям других исследователей [Trubikhin and Pilipenko, 2011]; [Radionova et al, 2012]; [Popov et al, 2013] Pilipenko, 2011], [Radionova et al, 2012], [Popov et al, 2013], , [Palcu et al, 2018]. [Cande, Kent, 1992]; [Popov et al, 1996]; [Gradstein et a., 2012].…”

From the Eastern Paratethys to the Pontocaspian basins

“…Characteristic examples of periods with positive water budget in the Eastern Paratethys are the middle Miocene (Karaganian) and the early Messinian (Maeotian). At that time, a climatically-driven increase of precipitation provoked transgressions that flooded the central and satellite basins of the Eastern Paratethys facilitating the migration of brackish water faunal communities (Popov et al, 2006;Palcu et al, 2019b).…”

“…• Isolation of the Eastern Paratethys, and following depletion of marine ecosystems that culminated in massive extinction during the Khersonian drying between 12.65 and 7.65 Ma (Iljina et al, 1976;Kojumdgieva et al, 1989;Lazarev et al, 2019 (submitted); Palcu et al, 2019b).…”

“…The most substantial base level drop occurred in the Khersonian regional stage and was responsible for whipping out the last marine faunal groups in the basin (Iljina et al, 1976;Paramonova, 1994). The succeeding climatically-driven Maeotian transgression refilled the basin and facilitated the spreading of brackish water faunas across the Eastern Paratethys (Popov et al, 2006;Palcu et al, 2019b). At the end of Maeotian, a short influx of marine microfauna known as "Pontian "flooding" characterizes the establishment of a short connection with the global ocean van Baak et al, 2016).…”

“…Het Dacische Bekken is een voorland van het Karpatengebergte en vormde tijdens het laat Mioceen het meest westelijke uiteinde van de oostelijke Paratethys. In die tijd leidde het samenspel van paleoklimaat en regionale tektoniek tot de isolatie van de oostelijke Paratethys van de open oceaan (De Leeuw et al, 2010;Leever et al, 2010;Popov et al, 2010;Palcu et al, 2015;De Leeuw et al, 2018;Palcu et al, 2019b;Simon et al, 2019). De daaropvolgende disruptie van het hydrologisch budget resulteerde in sterke fluctuaties in het water niveau, saliniteit, fauna en ecosystemen (Karami et al, 2011;Vasiliev et al, 2015;Simon et al, 2019).…”