Cenomanian-Campanian (Late Cretaceous) planktonic assemblages of the Crimea-Caucasus area: Palaeoceanography, palaeoclimate and sea level changes

摘要

During the Cretaceous, the Crimea-Caucasus area occupied a position in the Peri-Tethys which was transitional between the Boreal and Tethyan realms. The evolution and stratigraphic distribution of planktonic foraminifera and radiolarians in the Upper Cretaceous sediments of the region are described. The specialized, morphologically complex keeled taxa evolved in the latest Albian and persisted until the end of the Cretaceous. These overall evolutionary trends are punctuated by a series of bioevents, one of the most important being the Cenomanian-Turonian boundary. This is marked by a series of organic-rich sediments, that are related to an Oceanic Anoxic Event. The Turonian-Coniacian interval was marked by a further development of keeled taxa. A major change in the assemblage is described near the Santonian-Campanian boundary, when marginotruncanids were replaced by globotruncanids.