RIFT FORMATION IN THE GAKOVA REGION, SOUTHWEST ANATOLIA - IMPLICATIONS FOR THE OPENING OF THE AEGEAN SEA

The time of the onset and the nature of the extension in the Aegean area have been problematic owing to the confusion of neotectonic replacement structures with neotectonic revolutionary structures. This paper concerns two rift systems of different ages and orientations in the Gokova region of southwestern Anatolia. The first system has a northwest-southeast trend with a Middle to Upper Miocene infill, whereas the second system is orientated in an east-west direction and filled with Plio-Quaternary rocks. Structural and palaeomagnetic data indicate that the first system originally had a north-south trend, and then bodily rotated anticlockwise to its present orientation before the end of the Miocene. Both the orientations and the structural patterns of these cross-cutting rift systems suggest that they resulted from two different and successive tectonic regimes. Regional geology suggests that the generative regime of the older system was characterized by north-south compression and related to the palaeotectonic evolution of southwestern Anatolia, whereas that of the younger system is characterized by north-south extension and relates to the neotectonic evolution of this region. This inference contradicts, at least in southwestern Anatolia, some recent claims that the extensional tectonics and the related rift formation in the Aegean region began in the early Miocene, with the alleged demise of the compressional palaeotectonics during the late Oligocene,but is consistent with older views that placed the onset of north-south extension into the later middle Miocene. The formation of the Aegean Sea seems to be the result of these two complicated and contrasting, succesive tectonic regimes that have affected this region since middle Miocene times

Structural patterns of the Lake Erçek Basin, eastern Anatolia (Turkey): evidence from single-channel seismic interpretation

This study presents an analysis of the single-channel high-resolution shallow seismic reflection data from Lake Ercek, eastern Anatolia, to provide key information on the deformational elements, on the fault patterns and on the overall tectonic structure of the Lake Ercek Basin. High-resolution seismic data reveal major structural and deformational features, including N-S trending normal faults and W-E trending reverse faults bounding the Lake Ercek Basin, basement highs and folded structures along the marginal sections of the lake. The N-S trending normal faults asymmetrically control the steep western margin and the gentle eastern deltaic section, while the W-E trending reverse faults appear at the northern and southern margins. The N-S trending normal faults, half-graben structure, and the gradual thickening of sediments in the Ercek Basin toward the fault scarps strongly suggest an extensional tectonic regime resulting from an N-S compression. The Ercek Basin is an extension-controlled depocenter; it is a relatively undeformed and flat-lying deep Basin, forming a typical example of the half-graben structure. The N-S trending normal faults appear to be currently active and control the lake center and the E-delta section, resulting in subsidence in the lake floor. In the N- and S-margins of the lake, there is evidence of folding, faulting and accompanying block uplifting, suggesting a significant N-S compressional regime that results in the reverse faulting and basement highs along the marginal sections. The folding and faulting caused strong uplift of the basement blocks in the N- and S- margins, subsequently exposing the shelf and slope areas. The exposed areas are evident in the erosional unconformity of the surface of the basement highs and thinned sediments. The tilted basement strata and subsequent erosion over the basement block highs suggest prominent structural inversion, probably long before the formation of the lake. New high-resolution seismic data reveal the fault patterns and structural lineaments of the Lake Ercek and provide strong evidence for an ongoing extension and subsidence. The present study provides new structural insights that will support future tectonic and sedimentary studies and the development of strategies related to active earthquake faults and major seismic events in the region of Lake Ercek