PALEOZOIC SEDIMENTARY BASIN EVOLUTION AND OIL FIELDS, SE ANATOLIA, TURKEY

The aim of this presentation is to understand the paleogeographic evolution of Paleozoic sedimentary successions of the Southeastern Anatolian region in Turkey. In order to understand the development of the sedimentary basin of the region, well data, field observations and sedimentary features of the neighboring countries were evaluated. The SE Anatolian region is a geological continuation of the Arabian plate to the north. We have examined the development of the Mardin-Kahta uplift and time-environmental relations of Cretaceous and older sedimentary depositions in this region. We have used detailed biostratigraphical data, obtained from the wells and stratigraphic sections, of the Cambrian and Ordovician age depositions to constrain the age of the Mardin-Kahta uplift. We also have investigated various geologic sections in the stratigraphic–time tables and distribution maps to detect the possible effects of the Mardin uplift on the platform.

Deposition in the Southeastern Anatolian region was continuous and uniform throughout the Cambrian, but there were paleogeographical differences and stratigraphical gaps from the beginning of these deposits. According to the relation of the Ordovician and Cambrian deposits in the region, the Mardin uplift was active from the early Ordovician onwards. The distribution of the Ordovician deposits in the region indicates the geometry of the uplift. This NW-SE-directed uplift divided the Southeastern Anatolian Platform into Diyarbakýr and Akçakale basins, and controlled all the deposition on the platform until Cretaceous time. The Mardin-Kahta uplift was covered by a late Ordovician Sea in the Mardin region and maintained its continental condition until the Cretaceous in the Kahta region, and Cretaceous sediments were deposited directly on the Precambrian units. The Akçakale basin, which is located in the west-southwest of the Mardin-Kahta uplift, contains Cambrian, Ordovician, Devonian and Triassic-Jurassic sedimentary sequences. Open marine conditions persisted in this basin throughout the early Ordovician-Cretaceous.

From the Devonian to the late Permian there was another active uplift near the Siirt area (Siirt-Nusaybin Line), which separated the Hakkari basin from the Diyarbakýr basin to the north. The Hakkari sub-basin is represented by the Cambrian, Ordovician, Late Devonian-LowerCarboniferous,cPermian and Triassic-Jurassic depositional successions. The Diyarbakýr basin, which is in the west-northwest part of the Mardin-Kahta uplift, was active from the early Ordovician to the Cretaceous and consisted of Cambrian, Ordovician, Silurian-Devonian, Permian and Triassic-Jurassic sedimentary successions. Sediments in the Diyarbakýr basin were the source-rock for Ordovician, Silurian and Upper Devonian-Lower Carboniferous deposits and reservoir-rock for the Ordovician and Devonian deposits.

All these tectonic units described from the Southeastern Anatolian Platform are the extension of the main tectonic features of the Paleozoic Widyan and Tabuk Basins in the Arabian Plate.