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Marco Taviani, ISMAR-CNR (Italy)
Lorenzo Angeletti, ISMAR-CNR (Italy)
Namik Cagatay, Istanbul Technical University (Turkey)
Luca Gasperini, ISMAR-CNR (Italy)
Alina Polonia, ISMAR-CNR (Italy)
Frank Wesselingh, National Museum of Natural History, Department of Palaeontology Naturalis (Netherlands)
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Our understanding of the late Quaternary paleogeography of the region connecting the Black and Mediterranean seas is still rather fragmentary and its full appreciation requires the careful and integrated analysis of a variety of marine and non-marine records. At present Gemlik Bay is a shallow-marine (ca < 100 m depth) embayment separated from the Marmara Sea by a ∼50 m-deep-sill. During cruise MARM05 of R/V Urania, two gravity cores were collected at a depth of 76 m, Lat. N 40°23.82587', Long. E 29°01.99450', close to a trans-tensional branch of the North Anatolian Fault system, that expose a ∼10 m of late-Quaternary sediments. The cored sequence consists of a basal non-marine unit capped by less than 1 m thick fully marine deposits that mark the postglacial transgression in this region. The diverse mollusc assemblage associated with the basal unit contains lacustrine species of Ponto-Caspian affinity (i.e.: Micromelania cf lincta, Monodacna cf pontica, Monodacna cf colorata, Dreissena caspia, Dreissena bugensis etc.). One shell of Micromelania lincta was C14-AMS dated providing an age of 15860±90 yr BP (uncal). This macrofossil assemblage documents that the Gemlik Bay was at that time a non-marine Caspian-like (i.e., not in communication with the open sea) water body. The age seems to correspond to an episode of Caspian overflow into the Black Sea Basin, the so-called Early Khvalynian floods.
There are three spills between 14000 and 17000 yr BP. These overflows also are portrayed to have extended into the Bosphorus region and into the Propontida Basin. In general this phase corresponds to the Neoeuxinian in the Black Sea. The presence of the Caspian fauna to the south of the Black Sea clearly shows that during the Neoeuxinian the entire basin was shortly occupied by Caspian taxa. After the marine flooding Caspian taxa became restricted to the margins of the Black Sea (e.g.: Monodacna pontica, Micromelania spp., etc.).
The occurrence above these layers of sediments containing the brackish molluscs Ventrosia ventrosa and Cerastoderma glaucum mixed with reworked Caspian elements is a possible indication that the Marmara Sea reached the level to turn the Gemlik 'lake' into a shallow brackish lagoon. The existence of non-marine Caspian (then brackish?) conditions was terminated by the flooding of seawater from the Marmara Sea linked to glacio-eustatic sea level rise testified in our cores by a muddy infralittoral marine assemblage dominated by Corbula gibba and Turritella communis.
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