The tectonic influence on the last 1500-year infill history of a deep lake located on the North Anatolian Fault: Lake Sapanca (N-W Turkey)

Abstract

Lake Sapanca on the North Anatolian Fault zone (NW Turkey) is a pull-apart basin at the junction between the İzmit-Sapanca fault segment, the Sakarya segment and the westernmost end of the Mudurnu Valley fault. Multiproxy analyses of a 586-cm-long sediment core taken in the lake centre have revealed a complex history of earthquake events. The radiocarbon chronology, affected by reworking of plant remains, suggests that the sediment sequence retrieved from the centre of the lake covers approximately the last 1500 years. The bottom metre of the sequence is a gley soil indicating that at least the eastern half of the lake was a wetland, a prolongation of the floodplain between the lake and River Sakarya, that has collapsed to form the modern deep lake. A series of sedimentological and palynological indicators have been used to highlight four major episodes of mass movements linked to earthquakes. The short existence of the eastern part of the lake highlights the complexity of the morphology of the Sakarya Straight, a possible past connection between the Gulf of İzmit and the Black Sea.