Late quaternary sedimentation in the strait of bosporus: high-resolution seismic profiling

Date

1989-10

Author

Alavi, Seyed Naeim
Okyar, Mahmut
Köse, Timur

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Uniboom profiling supported by borehole data in the southern part of the Bosporus revealed that close to its banks Holocene sediments are underlain by the faulted slopes of a valley cut in many places into the Palaeozoic bedrock. Away from the banks the sediments thicken and their boundary with the underlying Pleistocene deposits is defined by an erosional surface at about the 80 ms TWT. This surface marks the initiation of marine currents in the valley as its deeper parts began to be submerged in the late Pleistocene to early Holocene (marine spillway phase). The upward-coarsening Holocene sequence records the subsequent evolution of the present two-way marine strait. The sequence is divided into three seismostratigraphic units. The lowest one constitutes an onlapping fill deposited under salt-wedge estuarine conditions when sediment input and runoff discharge were high and sealevel was still rising but the flow of Mediterranean waters into the Black Sea was not continuous. It fills low areas and is well developed under a sill close to the southern entrance of the Strait. As sealevel rose closer to its present level and the rate of terrigenous input decreased in the middle Holocene, this unit began to be eroded and reworked by strong bottom currents. The second unit records the transitional stage between the estuarine phase and the present two-layered current system. Its seismic facies and sedimentary features indicate deposition under high-energy conditions and shifting loci of accumulation. The third (surficial) unit is a thin depositional lag rich in shell fragments blanketing the other two units. It records deposition under fully marine conditions and flow of powerful bottom currents during the last few millenia.

Subject Keywords

Geology, Oceanography, Geochemistry and petrology

URI

https://hdl.handle.net/11511/51758

Journal

Marine Geology

DOI

https://doi.org/10.1016/0025-3227(89)90075-3

Collections

Graduate School of Marine Sciences, Article

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Citation Formats

S. N. Alavi, M. Okyar, and T. Köse, “Late quaternary sedimentation in the strait of bosporus: high-resolution seismic profiling,” Marine Geology, pp. 185–205, 1989, Accessed: 00, 2020. [Online]. Available: https://hdl.handle.net/11511/51758.