Paleomagnetic rotations in the circum-Marmara region, northwestern Turkey since the Late Cretaceous

Abstract

The Marmara region (northwestern Turkey) is located along the Alpine-Himalayan orogenic belt, and consists of tectonic fragments of the İstanbul Zone, the Rhodope Strandja Massif, the Sakarya Zone and the Thrace basin. The Middle Eocene-Lower Miocene sedimentary rocks of the Thrace Basin covers a large area over the Rhodope Strandja Massif. It has been reported that the İstanbul Zone began to migrate southward, away from the Moesia Platform, along the dextral Western Black Sea Fault to the west and the sinistral Western Crimean Fault to the east, post the opening of the Western Black Sea in the Late Cretaceous. The İstanbul Zone and the Sakarya Zone collided after the closure of the Intra-Pontide Ocean in the Early Eocene. In this study, the Upper Cretaceous–Oligocene sedimentary and volcanic rocks, sampled from 90 sites in the Marmara region, were used to examine the deformation history of the Marmara region since Late Cretaceous. Our palaeomagnetic data showed counterclockwise rotation of R ± ΔR = 33.2° ± 9.8° and R ± ΔR = 28.5° ± 6.8° in the Sakarya Zone, for periods of Late Cretaceous and Middle Eocene-Oligocene, respectively. Similar rotations were detected from the Middle Eocene to Oligocene rocks in the Thrace Basin and the İstanbul Zone. Our results indicate that the tectonic entities in this region were underwent a post-Oligocene counterclockwise rotation of ca. 27° due to the westwards movement of the Anatolian plate, regardless of fault affected block deformation.