--> ABSTRACT: Sedimentation Patterns in the Niksar and Erbaa-Tasova Pull-Apart Basins, North Anatolian Fault Zone, Turkey, by Harvey A. Cohen, Fred Watchorn, H. Serdar Akyuz, Aykut Barka; #91020 (1995).

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Sedimentation Patterns in the Niksar and Erbaa-Tasova Pull-Apart Basins, North Anatolian Fault Zone, Turkey

Harvey A. Cohen, Fred Watchorn, H. Serdar Akyuz, Aykut Barka

The Niksar basin of northern Turkey is an active pull-apart developed between right-stepping segments of the North Anatolian Fault Zone (NAFZ). It is floored by the meander plain of the Kelkit River--an axial drainage which currently hugs the basin's northern (faulted) margin. Exposures of older, deformed basin-fill sediments are characterised by coarse, gravity flow-dominated alluvial fans. Systematic variations in clast composition (Tertiary volcanic - Mesozoic limestone) and the frequency of soil horizons suggest the influence of both tectonic and climatic controls.

The adjacent Erbaa-Tasova basin exposes >400m of latest Miocene-Pleistocene sediments deposited during an earlier phase of pull-apart formation. Lateral alluvial fan, axial braided stream, and lacustrine/flood plain deposits can be identified. Except for the lacustrine facies, all of these units are directly analogous to modern deposits of the Niksar basin. On outcrop-scale, direct influence of faulting on sedimentation (e.g. wedge geometries or fault-controlled lithofacies) is not observed.

In both basins, deformation of the sediments is dominated by NW-SE trending extensional faults, consistent with right-lateral shear along the NAFZ. Gentle folds parallel to the boundary faults and rare reverse faults also occur. Faults with oblique offset and tight meso-scale folds are restricted to the immediate vicinity of strike-slip fault segments. Collectively, these two basins provide useful analogues for the drainage patterns, depositional systems and structural style of reservoirs developed in terrestrial pull-apart basins.

AAPG Search and Discovery Article #91020©1995 AAPG Annual Convention, Houston, Texas, May 5-8, 1995