Paleomagnetic results from Western Anatolia: evidence of microblock rotations after emplacement of the lower Miocene Yuntdağ volcanic rocks

Abstract

The eastern Aegean region has undergone north dipping subduction in the Oligocene, followed by continental collision in the early Miocene and then Miocene-Pliocene extension, which was associated with widespread Miocene volcanism. The aim of this study is to assess evidence of crustal block rotations due to stress variations in the Dikili (İzmir) province, Western Anatolia, based on paleomagnetic data obtained from 35 independent sites in addition to data from 19 sites reported in earlier studies. The lower Miocene Yuntdağ volcanic rocks were erupted in three different structural blocks, the Bergama, Zeytindağ and Dikili blocks. Clockwise rotation is found in the Dikili and Zeytindağ blocks that varies from R (± ∆R) = 12.5° (± 7.4°) in the west to R (± ∆R) = 35.6° ± (13.2°) in the east of the Bakırçay graben, respectively. In contrast, a counterclockwise rotation of R (± ∆R) = ‐38.1° (± 6.4°) is estimated for the Bergama block, to the north of the Dikili and Zeytindağ blocks. A scissor-like basin evolution is proposed during the opening of the Bakırçay graben which led to counterclockwise rotation of the Bergama block and clockwise rotation of the Dikili and Zeytindağ blocks after the early Miocene up to the Present. The rotation pattern derived from results of this study demonstrates that localized small scale deformation due to basin evolution besides regional affects must be considered as part of the deformation matrix in this area.