Major hydrological shifts in the Black Sea Lake in response to ice sheet collapses during MIS 6 (130-184 ka BP)

The Saalian was one of the largest glaciations during the Quaternary with an ice sheet extending considerably wider into the Eurasian continent than during other glacials. Orbital variations caused the ice sheet to switch between growing and shrinking. The partial retreat of the ice sheet and meltwater discharge resulted in global sea-level rise and increased lake levels of inland seas with broader environmental implications. During Marine Isotope Stage 6 (MIS 6), meltwater entered the formerly enclosed Black Sea at least twice as documented in a delta O-18 record from Anatolian speleothems. Here we present a sedimentary record from the Black Sea Lake covering MIS 6 and provide evidence for three meltwater periods coinciding with insolation maxima (BSWP-6-1: 180-167 ka BP, BSWP-6-2: 160-145 ka BP, BSWP-II: 133-130 ka BP). While delta O-18(ostracods) and Sr/Ca-ostracods point to pronounced meltwater supply and decreasing salinity, Sr-87/Sr-86(ostracods) shed light on meltwater sources and pathways. During all three periods, meltwater drained most likely via the Dnieper and Volga into the Black and Caspian Seas and connected both basins. Relatively low Sr-87/Sr-86(ostracods) values during the oldest meltwater period suggest melting solely of the eastern Eurasian Ice Sheet. In contrast, during the younger meltwater periods, exceptional high Sr-87/Sr-86(ostracods) values point towards additional meltwater from the western Eurasian Ice Sheet. A surplus from melting glaciers in the Tian Shan and Pamir Mountains that finally entered the Caspian Sea via the Amu Darya and Sry Darya probably amplified the input of high radiogenic Sr-isotope water. We also show that higher temperatures and productivity suggest Dansgaard-Oeschger-like climate variability during the first half of MIS 6. (C) 2019 Elsevier Ltd. All rights reserved.