Western Extension of the North Anatolian Fault and Associated Structures in the Gulf of Saros, NE Aegean Sea

Abstract

Western extension of the North Anatolian Fault (NAF) and associated structures were investigated in the Gulf of Saros using offshore seismic reflection and onshore field studies. The northern branch of the NAF, the Ganos Fault, extends westwards from the Sea of Marmara and splays into many branches in the Gulf of Saros. These faults are dextral strike-slip dominated oblique faults with normal displacements, and have played a major role in the formation of a 700-m deep, wedge-shaped, asymmetrical graben structure of the gulf. The main branch (the Saros-Ganos fault) is the most active fault. It dips steeply northwards, forming the northern coast of the Gelibolu Peninsula with a steep escarpment. The Ganos Fault connects at depth with the Anafarta reverse fault in the Gelibolu Peninsula, forming a positive flower structure. This structure has resulted in the uplift of the northern part of the peninsula since early Pliocene. Another important structural element is the NE-trending folds in the Miocene-lower Pliocene sediments. The folds have probably formed in the transpression zones on the margins of the gulf during the late Pliocene-early Pleistocene. Stratigraphy of the sediment infill and the structures indicate that it was mainly during this time that the gulf started gaining its present asymmetric morphology. This was a period of escalated tectonic activity under the dextral NAF and the Aegean N-S extensional regimes. Uplift and erosion of the margins of the gulf continued until the late Pleistocene. An important change in tectonics of the gulf at about 200 kyr caused the northern margin to submerge and form the shelf.