Acoustic evidence of shallow gas accumulations and active pockmarks in the İzmir Gulf, Aegean sea

Dondurur, Derman; Çifçi, Günay; Drahor, Mahmut G.; Coşkun, Süleyman

doi:10.1016/j.marpetgeo.2011.05.001

Cited by 47 publications

(31 citation statements)

References 41 publications

(45 reference statements)

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“…Considering the Turkish coastal seas, several gas bearing regions have been discovered in the Black Sea (Ergün et al 2002, Çifçi et al 2003, Dondurur 2005, Aegean Sea (Bange et al 1996, Dondurur et al 2011 as well as in the Sea of Marmara (Zitter et al 2008). The gas seepage and fluid escapes in the Sea of Marmara might have resulted from a combination of various factors, mostly associated with active tectonic features (Ritt et al 2010).…”

Section: Introductionmentioning

confidence: 99%

“…Many shallow biogenic gas reservoirs, associated mostly with the Late Quaternary deposits, have recently been discovered throughout the world (e.g., Judd and Hovland 1992, Okyar and Ediger 1999, Fleischer et al 2001, Ergün et al 2002, Garcia-Gil et al 2002, Gay et al 2006, Dondurur et al 2011) and successful efforts have been made for their exploitation. The main scope of present paper is to describe the distribution of gas bearing shelf sediments along the southern margin of the Sea of Marmara (Fig.…”

Section: Introductionmentioning

confidence: 99%

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

Vardar

Alpar

2016

Acta Geophys.

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A b s t r a c tHigh-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 km 2 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.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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

Vardar

Alpar

2016

Acta Geophys.

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“…In some areas, the chimneys below the pockmarks can be traced down to acoustic blanking zones (Figure 6(c)) and are interpreted as gas seeps. The hyperbolic distortions on the seafloor of the chirp data could be indicators of previous seep zones because of the existence of narrow high reflectivity columnar zones below them (Dondurur, Çifçi, Drahor, & Coşkun, 2011). They can therefore be used to identify inactive pockmarks ( Figure 5(a)).…”

Section: Pockmarksmentioning

confidence: 99%

Control of active faults and sea level changes on the distribution of shallow gas accumulations and gas-related seismic structures along the central branch of the North Anatolian Fault, southern Marmara shelf, Turkey

Okay

Aydemir

2016

Geodinamica Acta

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Detailed reviews of multichannel seismic reflection, sparker, chirp and multibeam data that were collected on the southern Marmara Sea shelf revealed various shallow gas indicators and related sedimentary structures, including enhanced reflections, seismic chimneys, acoustic blanking, bright spots, pockmarks, mound-like features and seeps. Seismic attribute analyses were applied to characterise the existence of gas-bearing sediments. The distribution of shallow gas indicators provides important insights into their origin and the geological factors that control them. Prominent gas accumulations and seeps are observed along the profiles that cross the branches of the central segment of the North Anatolian Fault Zone, which indicates that the gas seeps are controlled by active faulting. This indicates that the faults act as conduits through the sedimentary column. The dense occurrences of gas directly off the river mouths along the shallow bays provide clues about the organic-rich carbon content of the sediments and biogenic methane generation. In some areas, the gas-related acoustic anomalies are mostly located in the upper sediments below the marine unit, which indicates that the gas emissions in these areas were terminated as a result of the increased overburden pressure after the Holocene sea level rise and the deposition of the marine unit.

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“…The same can also be said about some natural offshore oil seeps. Lately, the seepage of methane and heavier hydrocarbons through the seafloor and through lake beds have achieved increasing scientific focus for various reasons (Niemann et al, 2005;Whelan et al, 2005;Judd and Hovland, 2007;Jensen et al, 2008aJensen et al, , 2008bWegener et al, 2008;Hovland et al, 2010;Plaza-Faverola et al, 2010;Valentine et al, 2010;Wessels et al, 2010;Brothers et al, 2011;Dondurur et al, 2011;Hammer et al, 2011;Krylova et al, 2011;Pape et al, 2011;Redmond and Valentine, 2011;Reitz et al, 2011;Solomon et al, 2011;Batang et al, 2012). One of the reasons is that scientists and the general public are becoming more concerned about the carbon cyclus, in general, and the radiative (greenhouse) gases in particular (Hovland et al, 1993;Kennett et al, 2000;Mienert et al, 2005;Etiope et al, 2008;Westbrook et al, 2009;Canet et al, 2010;Brett et al, 2011).…”

Section: Introductionmentioning

confidence: 99%

Methane and minor oil macro-seep systems — Their complexity and environmental significance

2012

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Acoustic evidence of shallow gas accumulations and active pockmarks in the İzmir Gulf, Aegean sea

Cited by 47 publications

References 41 publications

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

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

Control of active faults and sea level changes on the distribution of shallow gas accumulations and gas-related seismic structures along the central branch of the North Anatolian Fault, southern Marmara shelf, Turkey

Methane and minor oil macro-seep systems — Their complexity and environmental significance

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