International Geologiical Congress - Oslo 2008

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HPQ-02 Black Sea?Mediterranean Corridor during last 30 ky: Sea level change and human adaptation

 

The Holocene sedimentaton on the North Caucasian Black Sea Shelf: A response to sea level change

 

Elena Platonova, Moscow State University (Russian Federation)
Ivar Murdmaa, Shirshov Institute of Oceanology (Russian Federation)
Tomas Cronin, National Center US Geological Survey (United States)
Elena Ivanova, Shirshov Institute of Oceanology (Russian Federation)
Oleg Levchenko, Shirshov Institute of Oceanology (Russian Federation)
Vera Vasileva, Shirshov Institute of Oceanology (Russian Federation)
Steven Howe, University at Albany (United States)
 

 

We present here a renewed interpretation of our study results including high-frequency seismic survey and multiproxy studies of sediment cores obtained during the R.V. Akvanavt cruises 1999-2006) from a transect across the NE Black Sea shelf off the Arkhipo-Osipovka village. The sediment cover, 2 to 10m thick, consists of alternating mud and shell interbeds reflected as a stratified sequence in the seismic records. The sediment cover unconformably overlies lithified and folded Paleogene to Upper Cretaceous flysch. We hypothesize that shell deposits and corresponding seismic reflectors correspond to sea level lowstands, whereas Acoustically transparent mud beds in between indicate transgressive phases. The transgressive-regressive cycles revealed correlate with the data from near-shore and coastal areas. Core Ak-2571 from the shelf edge recovered a condensed section with both Caspian and Mediterranean mollusks in it's lower part. We refer it to transitional Vityazevian transgression phase, when saline deep water from Bosphorus inflow reached this shelf edge. It overlies the Neoeuxinianshell deposit (14C age 10500 yrs. BP) The Neoeuxinian-Vityazevian cycle is characterized by mixed mollusk assemblages reflecting a transition from semi-freshwater to brackish marine environments. Kalamitian transgressive sediments with Mytilus galloprovincialis and Chione gallina at the shelf edge and Modiolus phaseolinus on the outer shelf. demonstrate rapid mud accumulation (6900-6000 14C yrs.) Caspian elements in the faunal assemblages disappear. Sedimentation rates slow down about 4000 14C years ago. We refer this event to Kundukian regression phase also marked by a reflector and shell layer. Dzhemetenian sediments with Modiolus phaseolinus crown the section in the outer shelf, but the Phanagorian regressive phase (about 2600 14C yrs BP) marked by a shell layer and later Nymphean sediments possibly occur in shallower depths. The Holocene history of marine paleoenvironments documented by our Multiproxy core records and seismic profiles comprises two major stages with superimposed minor transgressive-regressive cycles: (1) the gradual glacioeustatic sea level rise by 40-50m; (2) oscillation around the zero level from 6000 14C yrs. BP to present. Corresponding submerged coastlines are distinguished by seismic records.

 

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