Clay mineral distribution in last Glacial-Holocene sediment cores from the eastern Marmara Sea (Çınarcık Basin–İzmit Gulf Transition), NW-Turkey: Multisources and transport paths in a two-way flow system

Abstract

The regional variations in grain size, XRD-bulk and clay mineral distribution in 97 sediment samples from 6 gravity cores obtained from 20 to 300 m water depths have been investigated to reveal source and transportation patterns as well as the effects of climatic and sea-level changes during the last 25,000 14C BP in the eastern Marmara Sea (EMS), NW Turkey. The major proportions of sediments in the EMS consist of silt (20–83%) and clay (17–90%), whereas sand and gravel abundances rarely exceed 10%. Of the bulk minerals, 10-Å micas (23–55%) and feldspars (17–55%) dominate over quartz (10–21%) and calcite (10–26%). Smectites (23–62%), illite (18–36%), chlorites (6–21%), kaolinite (2–20%) and 14S–14C mixed layer minerals (0–27%) constitute the principal clay mineral assemblages. Both bulk and clay mineral assemblages in the EMS are similar to those found in the İzmit Gulf, on the southern Marmara shelf, at the Marmara–Aegean approaches and the southern Black Sea. This would suggest that there is no distinct source for mineral assemblages of the study area outside the Marmara Basin. The concentrations of clay fractions and clay mineral assemblages tend to increase or decrease with depth in the cores, but this is limited to some intervals and not to entire sections in the cores. This distribution pattern therefore represents rather local sources of provenance and surrounding fluvial drainage basins together with dilution and distribution effects by current transport processes, rather than the expected paleoclimatic features and sedimentary input by inflowing Black Sea and Aegean Sea water masses throughout the last Glacial to Holocene.