Abstract
The Ganos Fault, a part of the Northern strand of the North Anatolian Fault system, is an active- strike slip fault and divides the narrow NW shelf of the Sea of Marmara into two parts near the town of Gaziköy. This paper presents recently collected shallow high-resolution seismic data to discriminate the sedimentary successions, each characterized by distinctive stratigraphic patterns on both sides of the Ganos Fault. Two main units, namely U1 and U2, and three para-sequences (U1a, U1b and U1c) were identified, depending on their internal reflection patterns, accommodation depths as well as the presence of conformity and the unconformity surfaces. The thickness of Unit U1 reaches its maximum at the northern side of the Ganos Fault; it is much thinner to the south. The para-sequences of U1b and U1c have “progradation” and “aggradation to progradation” depositional characters, respectively. This probably implies fluvial deposition controlled by sea- level fluctuations. Unit U1b can only be observed at the northern side of the Ganos Fault, while Unit U1c at the southern side. Units U1a and U1b were deposited during the transgressive system tract, while Unit U1c was deposited during a sea-level fall and/or a lowstand phase marked by an erosional surface. The marine terraces in the study area are shallower than those along the northern shelf of the Sea of Marmara, possibly due to successive tectonic displacements along the Ganos Fault, which also controls the distribution and thickness of the parasequences identified in this study.
Highlights
Fluctuations in global sea level and associated changes in sediment supplies are the primary effects that control the depositional conditions between shelves to continental margins through transgressive-regressive cycles
During the Last Glacial Maximum (LGM), for example, the Sea of Marmara turned into a lacustrine, and its shelves were sub-aerially exposed
The SB is characterized as an erosional unconformity at the depths shallow than -85 m; below this critical depth it is conformable with overlying sediments (Figure 2a, 2b). This implies that the erosional part of SB underwent subaerial conditions during the LGM lowstand
Summary
Fluctuations in global sea level and associated changes in sediment supplies are the primary effects that control the depositional conditions between shelves to continental margins through transgressive-regressive cycles. Water transfer from the Sea of Marmara to the adjacent seas (Black Sea and Aegean Sea), i.e. its paleooceanographic conditions in the late Quaternary, are controlled mainly by the morphology of the connecting straits (İstanbul and Çanakkale) in response to global sea level changes (Figure 1a). During the Last Glacial Maximum (LGM), for example, the Sea of Marmara turned into a lacustrine, and its shelves were sub-aerially exposed. It was a fresh/brackish water lake between early MIS4 to MIS1, and an important regression occurred during MIS 2 [Çağatay et al, 2015]. Connection was re-established with a transition to a warming period [Çağatay et al, 2009] between 14.7 cal kyr BP [Vidal et al, 2010] 12.55 ± 0.35 cal kyr BP [Çağatay et al, 2015]
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