Paleomagnetic evidence for upper plate response to a STEP fault, SW Anatolia

Abstract

Pliny-Strabo Trench is a Subduction Transform-Edge Propagator (STEP) Fault developed on the northern edge of the subducted African Oceanic Lithosphere. It connects the Aegean and Cyprian trenches in the Eastern Mediterranean convergent system. Although, deep geometry of the STEP fault and associated slab tear in mantle are imaged, its shallow vertical and lateral continuation in the crust and impact on the over-riding plate are still unknown. Thus, we have studied SW Anatolia, the candidate site where this structure could propagate laterally and vertically, for its vertical axis rotations using paleomagnetic tools. In this study, more than 2000 paleomagnetic samples were collected and analysed from 86 different sites which were later classified into 11 separate geographic domains displaying similar tectonic characteristics. Moreover, available paleomagnetic data in the literature were parametrically resampled, analysed and combined with our data. In the region, there is a positive correlation between rotation amounts and sample ages supporting continuous deformation throughout the Neogene period. The spatial variations of results indicated that the study area can be divided into three main domains based on vertical axis rotations. From the south to the north these domains include SW Anatolian domain with ∼20° counter-clockwise rotation, Burdur–Dinar–Ulubey domain with ∼4° counter-clockwise rotation and northern areas characterized by clockwise rotations. The identified domains of counter-clockwise rotation are separated by a well-defined NW-SE striking Acıpayam Transfer Zone and there is no differential rotation in agreement with the presence of NE-SW striking shear zone in the region. Therefore, we concluded that the Pliny-Strabo STEP Fault have not propagated into the over-riding plate as a shear zone. This implies that there is no evidence to support the presence of alleged Fethiye–Burdur Fault Zone as suggested, and its existence is dubious.