The Seaway Connection between the Sea of Marmara and the Mediterranean: Tectonic Development of the Dardanelles

Abstract

A basin consisting of alluvial-fan, fluvial clastics, and lacustrine sediments dating from the late middle Miocene was developed in the southern part of the Thrace Basin, Gelibolu Peninsula, and the northwestern part of the Biga Peninsula. This basin was controlled by a southeastern fault that lies parallel to the northwestern rim of the Biga Peninsula. Shallow-marine sediments that occur widely in the upper parts of the sedimentary sequence in the basin indicate an initial connection between the Sea of Marmara and the Mediterranean during the middle to late Pannonian, extending from southern Thrace to west of the Biga Peninsula. The Saros-Ganos segment, forming a branch of the North Anatolian fault, developed as a positive flower structure in the late Miocene to early Pliocene. This structural high obstructed the seaway connection around Saros Bay. Clastics, originating from this positive feature, filled the Dardanelles Strait area of today. A late middle Miocene fault that controlled the geometry of the basin from the eastern shoulder of the Biga Peninsula was reactivated as a right-lateral strike-slip fault during the late early Pliocene (Ezine-Sarkoy fault). Synthetic faults associated with this major tectonic structure caused the opening of the Dardanelles. This tectonism resulted in the reconnection of the Mediterranean with the Sea of Marmara. The ages of foraminifer, ostracod, and nannoplankton assemblages, determined from wells in the Gulf of Izmit, indicate intermittent instead of continuous connection. The oldest Mediterranean connection was in late Pliocene-early Pleistocene time, the next connection occurred in the early to middle Pleistocene, and the final connection occurred during the late Pleistocene to Holocene.