Varve Chronology: Estimated Rates of Sedimentation in the Black Sea Deep Basin

Abstract

Various varve types and their implication in estimating rates of sedimentation in the Black Sea Basin are discussed. Average modern denudation rates in the Black Sea source area are estimated at 0.063 mm/yr or about 100 t/km2/yr. The stripped detritus would yield a sediment blanket of 0.4 mm/yr if spread evenly over the entire bottom of the Black Sea. Siliceous and calcareous remains of planktonic production would give additional increment, raising the average thickness close to 0.5 mm/yr. This value is representative for steppe vegetation. At times of forest vegetation, the denudation rate is lowered by more than half. Applying compaction effects, and assuming similar orographic relationships for the Pleistocene, the mean rate of deposition is 20 cm/10^3 yr. Since slumping and turbidity currents would eventually carry the bulk of the detritus to the deep basin, the sedimentation rate would almost double there. At times of glacial melting and loess mobilization, sedimentation rates could be as high as 10 m/10^3 yr. Rapid subsidence of the basin floor would also induce pulses of turbidites.