Holocene sea-level oscillations and environmental changes on the Eastern Black Sea shelf

TitleHolocene sea-level oscillations and environmental changes on the Eastern Black Sea shelf
Publication TypeJournal Article
Year of Publication2007
AuthorsIvanova, EV, Murdmaa, IO, Chepalyga, AL, Cronin, TM, Pasechnik, IV, Levchenko, OV, Howe, SS, Manushkina, AV, Platonova, EA
JournalPalaeogeography Palaeoclimatology Palaeoecology
Date PublishedApr 6
Accession NumberWOS:000245637400004

A multi-proxy study of four sediment cores from the Eastern (Caucasian) Black Sea shelf revealed five transgressive-regressive cycles overprinted on the general trend of glacioeustatic sea-level rise during the last 11,000 C-14 yr. These cycles are well represented in micro-and macrofossil assemblages, sedimentation rates, and gain size variations. The oldest recovered sediments were deposited in the Neoeuxinian semi-freshwater basin (similar to 10,500-9000 C-14 yr BP) and contain a Caspian-type mollusk fauna dominated by Dreissena rostriformis. Low delta O-18 and delta C-13 values are measured on this species. The first appearance of marine mollusks and ostracodes from the Mediterranean is established in this part of the Black Sea at similar to 8200 C-14 yr BP, i.e., about 1000-2000 yr later than the appearance of marine microfossils in the deeper part of the sea. The Early Holocene (Bugazian to Vityazevian) condensed section of shell and shelly mud sediments with at least two hiatuses represent a high-energy shelf-edge facies. It contains a transitional assemblage representing a mixture of Caspian and Mediterranean fauna. This pattern suggests a dual-flow regime via the Bosphorus after 8200 C-14 yr BR Caspian species disappear and oligolialine species decrease in abundance during the Vityazevian-Prekalamitian cycle. Later, during the Middle to Late Holocene, low sea-level stands are characterized by shell layers, whereas silty mud with various mollusk and ostracode assemblages rapidly accumulated during transgressions. Restricted mud accumulation, as well as benthic faunal composition and abundance, suggest high-energy and well-ventilated bottom water during low sea-level stands. A trend of O-18 enrichment in mollusk shells points to an increase in bottom-water salinity during the Vityazevian to Kalamitian transgressions (similar to 7000 to 5700 C-14 yr BP) due to a more open connection with the Mediterranean, while a pronounced increase in polyhaline species abundance is established during the Kalamitian to Djemetean transgressions (similar to 6400 to 2700 C-14 yr BP). However, the composition of the faunal assemblage indicates that bottom-water salinity never exceeded modem values of 18-20 psu. (c) 2006 Elsevier B.V. All rights reserved.