Sedimentation processes in a tectonically active environment: the Kerkyra-Kefalonia submarine valley system (NE Ionian Sea)

Poulos, S.E., Lykousis, V., Collins, M.B., Rohling, E.J. and Pattiaratchi, C.B. (1999) Sedimentation processes in a tectonically active environment: the Kerkyra-Kefalonia submarine valley system (NE Ionian Sea). Marine Geology, 160 (1-2), 25-44. (doi:10.1016/S0025-3227(99)00016-X).

Abstract

The Kerkyra–Kefalonia valley system is the northwestern extension of the Hellenic arc–trench system, representing the collision zone of the Apulian Platform and the Hellenides. The system is distinguished by two different physiographic regions: the northern part, U-shaped, and oriented NNW–SSE, with relatively gentle slopes and a wide floor; and the southern part, oriented NE–SW, V-shaped, and with much steeper side walls and a narrow floor. Both parts are formed tectonically, with the former coinciding with a collision zone, and the latter being the morphometric expression of the Kefalonia strike–slip fault. Sediments recovered in the piston cores from the region consist of fine-grained material, deposited by a variety of sedimentation processes such as: gravity-driven mass movements, associated with seismic activity (i.e., slumping, sliding, debris flows, grain flows, turbidites–seismoturbidites); and, to a lesser extent, by hemipelagic deposition. Measured near-bed currents and their associated shear stresses indicate resuspension of the material, mainly within the northern part of the valley. Sub-bottom acoustic (seismic) profiling data reveal various sedimentary provinces, related to different mechanisms of sediment accumulation: (i) the eastern margin of the Apulian Platform with hemipelagic sedimentation, together with possible advection of suspensates from the Adriatic, in response localised to seabed erosion; (ii) the western Hellenic margin, with down-slope episodic sliding and slumping, induced primarily by earthquake activity, together with an input from hemipelagic settling; (iii) the collision zone, coinciding with the northern part of the Kerkyra–Kefalonia valley system, with deposition mostly from resuspension, the occurrence of local mass gravity flows and the advection of some material from the north; and (iv) the Kefalonia strike–slip fault region, where mass gravity flows are the dominant mechanisms, related to erosion/deposition from resuspension. Overall sedimentation within the tectonically-active Kerkyra–Kefalonia valley system is characterised by the coupling of the mass gravity-driven flows, which are the predominant mechanisms, with the near-bed current regime related with resuspension phenomena and the advection of suspensates. These latter mechanisms is likely more pronounced during the winter period, when dense water masses formed in the Adriatic inflowing into the Ionian Sea.

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Contributors

Author: E.J. Rohling

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