An oligocene sink for organic carbon: Upwelling in the paratethys?
Abstract A synoptic review of the organic carbon content, kerogen type, biogenic siliceous sediments and planktonic remains is attempted for the often anoxic Oligocene-Early Miocene sediments of the Paratethys covering a large area between the Rhine Valley and the Aral Sea. On this basis stratification of the sea and intensity of planktonic productivity are discussed for different parts of the Paratethys. The Eastern parathethys and some parts of the Central and Western Paratethys show a Black Sea-like stable stratificatin, while the bulk of the anoxic sediments in the Carpathian Flysch Basin are interpreted to have an upwelling origin. The supposed Flysch Ocean upwelling regime has no good recent analogue, although it shows similarities with the Bay of California (high rate of Corg burial, laminated, diatomaceous sediments, and turbiditic intercalations) and offshore NW-Africa (abundant fresh-water discharge). Sediments of a brackish-water incursion are widespread on the bottom of the NP 23 zone. From earliest Oligocene to Early Miocene a continuous narrowing of the anoxic sedimentary belt towards the East-European Platform is observed.