Date

1991-02-01

Author

ERGIN, M
BODUR, MN
EDIGER, V

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Surficial sediment samples collected from the northeastern and southwestern shelf regions of the Sea of Marmara, together with data available from other sources, indicate marked variations in sediment compositions resulting from differences in topographical, hydrological and biological conditions. In the strait channels of the Dardanelles and Bosporus, where strong undercurrents prevail, the floor was covered mostly by coarse-grained sediments (rich in sand and gravel). However, in areas of relatively low energy conditions, sediments contained appreciable amounts of mud, with a tendency towards an increase in the amount of clay towards the open sea. The effects of the strong undercurrents on the bedforms was also apparent in the southern Strait of Bosporus where sidescan sonar surveys revealed the presence of asymmetrical sand ripples. Although terrigenous mud is the principal sediment type in the two canyons (Dardanelles and South Bosporus), the sediments, in particular on the floor of South Bosporus Canyon, show a distinct contrast between the inner N-S and outer E-W trending parts: along its axis, where depths are greatest, the outer part of the canyon appears to contain much more coarse sediment (in part derived from the benthic communities) than the inner canyon. In general, both the topography-related current regimes and the biological activities in the study areas mostly determine the types and modes of sediment distribution. Among the biogenic components, the calcareous corraline algae Rhodophycae (chiefly Lithothamnium calcareum and L.fruticolusum) and the molusc families Galeommatacae and Cerithiospidae are associated with the prevailing Mediterranean undercurrents, especially in the shallower waters of the junction of the Sea of Marmara and Strait of Bosporus. The relatively abundant mollusc species Mytilus galloprovincialis and Modiolus barbatus and the Trochidae in the Strait of Bosporus are largely affected by Black Sea waters. The wide range of carbonate concentrations in the sediments generally reflects the relative abundances of biogenic admixtures in the samples. High carbonate percentages in the sediments are usually associated with low mud contents, and vice versa. Interestingly, the organic carbon contents of the sediments generally increase with proximity to the Black Sea, suggesting influxes of appreciable amounts of organic matter from the Black Sea.

Subject Keywords

Geology, Geochemistry and Petrology, Oceanography, Qaternary

URI

https://hdl.handle.net/11511/66761

Collections

Graduate School of Marine Sciences, Article