Denizhan Vardar

High-Resolution Seismic Characterization of Shallow Gas Accumulations in the Southern Shelf of Marmara Sea, Turkey

High-resolution seismic survey was conducted to investigate acoustic characteristics of gassy sediments along the southern shelf of the Sea of Marmara. The acoustic turbidity zones outlined within the study area are generally below 2–9 m (2-10 ms TWT) the seafloor whilst this vertical distance varies between 9 and 21 m (10–25 ms TWT) for acoustic blanket type reflections. The gassy sediments cover an area of sea floor of about 45, 110, and 75 km2 in front of Gönen River, Kocasu River, and Gemlik Bay, respectively. The gassy sediments in the center of Gemlik Bay exhibited an elliptical geometry similar to its basin while the others have deltaic forms in front of the rivers. The sea bottom and near surface sedimentary units are made-up of organic-rich sediments, mostly transported by the southern rivers. The gas observed in sediments is thought to be of biogenic origin, which may be caused by degradation of organic matter in the sediment.

Seismic stratigraphy and depositional history of the Büyükçekmece Bay since Latest Pleistocene, Marmara Sea, Turkey

High-resolution seismic data shed light on latest Pleistocene and Holocene sedimentation beneath the Büyükçekmece Bay, northern shelf area of the Marmara Sea, Turkey. Discontinuous fluvio-marine and marine deposits overlying the erosional truncation surface of Oligocene–Lower Miocene deposits are as thick as 30 m and preserved preferentially within the incised valleys that were controlled by some old faults. A series of prograding shoreline, laterally passing to the latest Pleistocene–Holocene valley-fill deposits, are thought to have accumulated mainly during times of shoreline transgression and sea-level rise. The overall morphology and stratigraphic setting observed in the Büyükçekmece Bay and at the southern outlet of the Bosphorus Strait have nearly same characteristics, implying that similar hydrodynamic conditions, erosional and depositional processes were mainly under the control of strong northerly flows during the Late Quaternary. These flows were less powerful in the Büyükçekmece region with decreased sediment input and smaller accommodation space.

Active tectonics and deformation patterns evidenced from new Chirp seismic data from Marmara Sea, Turkey

Summary The northern branch of the North Anatolian Fault (NAF) zone is the most active tectonic element in the Marmara Sea and responsible for most of the seafloor and subsurface deformations observed along the northern shelf. Various of these deformations are determined by using Chirp data. In this context, Chirp seismic data were conducted in 2015. A total of 500 km Chirp data have been interpreted to reveal the structural features of the basement rocks covered with late Quaternary sediments along the northern shelf. The sediment thickness of the thin overlying seismic unit (U2) increases close the coastline and beyond the shelf break. The lower unit (U1) gradually thins in the middle of the shelf and towards the shelf break in the study area; mostly under the control of the terraces observed on top of the U1. All faults and tectonic deformation have only been observed under this Holocene unit. It is merely observed tectonic features (folding, undulation, faults) in the U1. The Holocene unit covered not only the tectonic structures and faults below the truncational erosion surface but also the older lithology, mainly folded and sometimes tightly folded.. The faults in the lower unit actually have low seismic activity.