High-resolution total field magnetic anomaly maps of Lake İznik (NW Turkey): assessment of faults which play important roles in tectonics of the lake

In total, 380 km of marine magnetic data were processed and interpreted to reveal the main tectonic elements that control the formation of the lake. Lake İznik, which is an approximately rectangular-shaped active tectonic basin with 32 km length and 12 km width, is located between two segments of the North Anatolian Fault in the northeast Marmara region, Turkey. The purpose of this study is to identify the tectonic elements that played a role in the formation of Lake İznik with the help of new magnetic data and to reveal the tectonic evolution of the region by using other previously collected geophysical data. The Euler deconvolution, tilt angle, analytic signal and source edge detection methods were applied to the total field magnetic data for Lake İznik and its surroundings to determine the boundaries and depths to the source of magnetism. From the structural map obtained as a result of the review of this data, linearity in the magnetic data was detected along the NW–SE direction in the north of Lake İznik, N–S direction in the west and east, and E–W direction in the south. These lineaments were correlated with a limited amount of seismic data obtained from previous studies and were associated with faults. This linearity in NW–SE direction in the north was evaluated as the continuation of the Orhangazi fault and it is thought to play a significant role in the tectonic evolution of Lake İznik. When the results obtained from this study and the paleomagnetic results for the Eocene volcanic rocks in the study area are evaluated together, Lake İznik was connected with Gemlik Bay and the Marmara Sea during the Eocene–Pleistocene and Orhangazi Fault disconnected Lake İznik from Gemlik Bay in the Pleistocene–Holocene. It was deduced that the lake basin is a pull-apart basin developed up to the present day.