Last Glacial - Holocene stratigraphic development at the Marmara Sea exit of the Bosphorus Strait, Turkey
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ORIGINAL RESEARCH PAPER
Last Glacial - Holocene stratigraphic development at the Marmara Sea exit of the Bosphorus Strait, Turkey Kerem Ko¨pru¨lu¨1 • Bedri Alpar2
•
Denizhan Vardar2
Received: 19 October 2015 / Accepted: 16 February 2016 Ó Springer Science+Business Media Dordrecht 2016
Abstract High resolution Chirp and Sparker data allowed definition and mapping of distinct seismic units in the shallow sediment record (*100 ms) acquired from the southern exit of the Bosphorus Strait; a dynamic depositional environment. The bottommost unit observed in the Chirp data (unit-3) is made up of marine-lacustrine sediments thinning seaward and onlaps the basement rocks which are represented by folded strata in the Sparker data, possibly lower to middle Pleistocene age. It is overlain by a series of prograding deposits along the shelf (unit-2) referring to sediment input from the northern sector depending on the water levels of the paleo Marmara lake’s during MIS 3. The uppermost deposits (unit-1) close to the Bosphorus Strait were represented by three separate subunits, unlike to relatively thin drape of sediments observed at the other places in the surrounding regions. The detailed definition of these subunits deduced from the closelyspaced reflection profiles and available radiocarbon ages helped to explain the history of the latest stratigraphic development depending on the connections between the Black Sea and the Sea of Marmara. In addition to the previously proposed major conduits, which controlled the sedimentary deposition at the southern exit of the Bosphorus, namely the Bosphorus Strait and Kurbag˘alıdere & Bedri Alpar [email protected] Kerem Ko¨pru¨lu¨ [email protected] Denizhan Vardar [email protected] 1
Barajyolu Cd. 21 Atas¸ ehir, 34779 ˙Istanbul, Turkey
2
Institute of Marine Sciences and Management, ˙Istanbul University, 34134 Vefa, ˙Istanbul, Turkey
River, another submarine sedimentary pathway at the eastern bank of the strait’s channel seems to have delivered sediments directly into the basin. Keywords High-resolution seismic Lacustrine–marine transition Bosphorus strait Dardanelles sill Sea of Marmara
Introduction The Sea of Marmara (Fig. 1a) experienced fluctuations in sea level, which were partly in accordance with the global glacial–interglacial cycles, controlled by the connecting straits (Aksu et al. 1999). The average depth of the sills in the Dardanelles (C¸anakkale) Strait is about 70 m at present, even though various discontinuities, deep erosions and narrow paleo valleys (1 km) have been observed on the available seismic data (Yaltırak et al. 2000; Go¨kas¸ an et al. 2008, 2010). To the north, sea level in the Black Sea is mainly controlled by climate changes (Ryan 2007; Wegwerth et al. 2014, 2015). The water exchange with the Black Sea is controlled largely by the sedimentation and erosion within the Bosphorus (I˙stanbul) Strait, which is another outlet of the Sea of Marmara (Genov 2009). In this framework the paleoenvironmental evolution of the Sea of Marmara, the t
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