EXTENSIONAL STRUCTURE AND FAULT KINEMATICS OF THE LATE CENOZOIC ALASEHIR SUPRADETACHMENT BASIN IN WESTERN ANATOLIA, TURKEY

The Alasehir supradetachment basin (ASDB) developed during the late Cenozoic exhumation of the Menderes metamorphic core complex (MCC) in western Anatolia, Turkey. Four different fault generations controlled its evolution since the early Miocene. The E-W-striking, N-dipping low-angle Alasehir detachment fault (F1) separates high-grade MMC rocks from the Neogene deposits of the ASDB in the hanging wall. Synthetic and antithetic high-angle normal faults (F2) crosscutting the ASDB strata and MCC units caused tilting and back-rotation of the sedimentary strata. Low-angle normal faults (F3) both in the ASDB and MCC display crosscutting relations with F2 faults. N-S-striking, high-angle scissor faults (F4) were responsible for rotational deformation in the basinal strata and differential uplift of the MCC crystalline rocks in the footwall of the detachment fault. We have defined six individual, rotational fault blocks within the ASDB. Dip directions and strike orientations of the ASDB rocks change significantly within the individual rotational fault blocks. Relatively higher dip angles in the lower to upper Miocene Acidere and Gobekli units indicate higher amount of rotational deformation in the southern section of ASDB. Higher dip angles in the lower to upper Miocene units in comparison to shallower dip angles in the Plio-Pleistocene Yenipazar and Asartepe units are a result of progressive rotational deformation along F2 and F4 faults. The amount of extension associated with F2 faulting within ASDB ranges from 5% to 75%. Crosscutting relationships between F2 and F3 faults indicate that high-angle normal faulting was a continuous mode of extension as the MCC continued its exhumation during the late Cenozoic. Distribution of four different fault generations and their kinematics affected the shape and depth of the accommodation space in the ASDB, and controlled the deposition patterns and drainage systems in the basin. Local unconformities developed as a result of differential extension and block uplift within the basin. There is no evidence for large-scale contractional folding and for significant changes in the stress regime during the evolution of the ASDB, ruling out the possibility of a pulsed-extension history in the region.