Neogene quaternary evolution of the Eastern Marmara Region, Northwest Turkey

Three main stages have been distinguished in the Neogene-Quaternary morphotectonic evolution in the East Marmara region. They are Early-middle Miocene, Late Miocene-Pliocene and Latest Pliocene-Present. Three different sedimentary sequences, each overlies the other with an angular uncomformity, have been formed in these stages. Early-middle Miocene sedimentary sequence is characterised by continental detritics whereas the Late Miocene-Pliocene rocks are represented by continental to marine transitional sediments. Terrestrial-marine sediments have been deposited since the latest Pliocene till Present. The region was transformed to denudational area by the closure of the Intra-Pontid Ocean in the end of the Oligocene and it was under the effect of paleotectonic events during the early-middle Miocene. In the end of this erosional period which lasted until the end of middle Miocene, a peneplain morphology covering large area was formed and terrestrial sediments were deposited. Neotectonics which has affected actual geology in the region, initiated in the beginning of late Miocene and occurred in two stages which differ tectonic styles. In the late Miocene-Pliocene time, the region was affected by N-S directed compressional regime and it was uplifted by NE-SW and NW-SE trending strike-slip faults with E-W lying folds as a result of this compression. During this stage, a Late Miocene-Pliocene sedimentary sequence which starts with fluvial sediments at the bottom and passes into lacustrine to marine at the top, was deposited. In the end of the period, depressions in which late Miocene- Pliocene sediments were deposited, were spread out and the region was formed as a denudational area in the late Pliocene. The second stage of the neotectonic period covers a time interval from the Latest Pliocene to Present and it begun with the occurrence of the North Anatolian Fault. Actual morphology and active tectonic frame of the Eastern Marmara region were developed in this time interval which is known with the transform character of the North Anatolian Fault. However, structural evolution of actual Marmara sea region which is related to North Anatolian Fault, initiated in Latest Pliocene.