Mineralogy of Holocene Sediments from the Southwestern Black Sea Shelf (Turkey) in Relation to Provenance, Sea-level and Current Regimes

摘要

Grain size and mineral composition of core sediments were used to investigate influences of various terrestrial and marine conditions, which have prevailed on the southwestern Black Sea shelf during the Holocene. Siliciclastic mud with small amounts of sand and gravel from nearby coastal hinterland is the principal sediment type, whereas sediments deposited near the shelf edge and the ?stanbul Strait and off the Duru Lake (a paleo-river mouth) constitued large quantities of sand and gravel of both biogenic and terrigenic origin. Variable amounts of aragonite, 1 nm-micas, quartz, feldspars, calcite and dolomite constitute the dominant non-clay minerals in bulk sediments. The clay mineral assemblage in the < 2 μm fraction is made up of smectite, illite, kaolinite and chlorite. Aragonite and calcite are mainly derived from benthic accumulations, whereas feldspars (mainly plagioclase) and smectite reflect magmatic-volcanic provenance and the distribution of 1 nm-micas and chlorite correlate with nearby metamorphic sources onland. Nevertheless, grain size and mineral distribution generally indicate a combination of effects of wind and wave climate, longshore and offshore cyclonic currents, changing sea-level stands and nearby source rock and morphological conditions. It is also suggested that at least part of clay minerals could be derived from the northwesterly Danube River input.