Oya Algan

Morphologic features of the Marmara Sea from multi-beam data

Abstract The bathymetrical image of the Marmara Sea (NW of Turkey) was prepared, using data from mainly multi-beam surveys and from various other sources. The Marmara Sea presents a unique and complicated morphological system, which is mainly controlled by the active tectonic regime of the North Anatolian Fault Zone (NAFZ). The sub-bottom morphology of the Marmara Sea consists of a wide shelf area (55% of the total area) and the Marmara Trough, which includes the slopes, ridges and deep basins. The four basins separated by ridges constitute the E–W trending Marmara Trough in an elliptical form. Submarine canyons and landslides constitute the secondary morphological units of the Marmara Sea. The angle and the shape of the slopes are variable in different parts of the Marmara Sea. The linear-shaped slopes bounding the Cinarcik Basin (eastern extremity of the Marmara Sea) and off the Ganos Mountain System (west of Marmara Sea) are characteristic with their high gradient, and resulted from strike–slip fault. The curve-shaped slopes with low angles are considered to be associated with normal fault. E–W-aligned lineaments are morphological expressions of strike–slip faults and can be traced from the Ganos Mountain System through Cinarcik Basin, cutting through the basins and ridges in the western Marmara Trough, and bounding the Cinarcik Basin at the slope–basin transitions. These lineaments reflect a new rupture of NAFZ and must have occurred after the formation of the Marmara Trough.

Palynology of sapropelic layers from the Marmara Sea

Palynological records of the sediments from the deep basins of the Marmara Sea revealed four palynological zones indicating the changing climatic conditions during Late Glacial to Holocene. The lower two zones were defined by the high abundance of Artemisia and Chenopodiaceae that suggest the climate of the source area was cold and arid. However, the establishment of Mediterranean warm and wet climate and corresponding regression of continental aridity were shown by the decreasing Chenopodiaceae and increasing pollen grains of humid-type vegetation in Zone C. The highest total pollen with the dominance of Quercus identifies the deglaciation and coincides with the formation of sapropelic layers in the Marmara Sea. The warmer and humid condition of deglaciation was indicated with diversified moisture-demanding deciduous and coniferous pollen grains in Zone B. These pollen assemblages and their distribution pattern indicate that the source area was warm and wet, during the deposition of sapropelic layers in the Marmara Sea, and also reflect signals of Black Sea origin.

Variability of clay-mineral composition on Carolina Slope (NW Atlantic) during marine isotope stages 1–3 and its paleoceanographic significance

Abstract The clay-mineral composition of marine isotope stages 1–3 sediments at the Ocean Drilling program (ODP) Site 1055 on the Carolina Slope consists mainly of illite, kaolinite, chlorite and smectite. Clay-mineral variability is marked by a distinct increase in the relative amounts of kaolinite and smectite during the Holocene and by high illite and to a lesser extent chlorite relative amounts during marine isotopic stages 2 and 3. This grouping of clay minerals as two different assemblages during different isotopic stages suggest their different source affinities. The increase in the ‘kaolinite+smectite’ assemblage in the Holocene is accompanied by a significant increase in the sedimentation rate. The change in the sedimentation regime after the Last Glacial Maximum is interpreted to be related to resuspension and advection of clays and silts by increased deep water activity over the Bermuda Rise, followed by their transport to Site 1055 on the Carolina Slope by shallow elements of the North Atlantic Deep Water. High amplitude variations with high illite amounts characterize marine isotope stage 3 and appear to be related to Heinrich events.