Middle Eocene paleomagnetic data from the eastern Sakarya Zone and the central Pontides: Implications for the tectonic evolution of north central Anatolia

Abstract

A paleomagnetic investigation has been carried out on Middle Eocene volcanic rocks at 23 sites in the eastern Sakarya Zone and the central Pontides of north central Anatolia in order to better understand the regional tectonic evolution of the main zones of northeastern Anatolia in the Middle Eocene. The results constrain the tectonic evolution of the area when evaluated in conjunction with earlier published paleomagnetic directions from 92 localities. Small counterclockwise rotations in the range of R ± ΔR = −1.3 ± 1.4° to R ± ΔR = −17.2 ± 16.8°, with respect to Eurasia, are observed in the central Pontides on the northern side of the North Anatolian Fault (NAF). Clockwise rotations ranging between R ± ΔR = 8.5 ± 15.1° and R ± ΔR = 29.7 ± 12.0° are observed between the NAF and the Sungurlu Fault (SF), in the eastern Sakarya zone. Counterclockwise rotations of R ± ΔR = −18.9 ± 12.4° to R ± ΔR = −42.2 ± 6.9° are observed to the south of the SF. Our findings, combined with previous data, support the indentation model of Kaymakcı et al. (2000, 2003a, 2003b), which postulates the collision and northeast directed indentation of the Kırşehir Block into the Sakarya Zone. This model, which was developed to explain the evolution of the Çankırı Basin, can also explain the variable magnitudes of paleomagnetically determined rotations, thrust directions, and the curvature of the North Anatolian ophiolite belt.