Seismic evidence of shallow gas from Lake Van, eastern Turkey.

Cukur, Deniz, Krastel, Sebastian, Tomonaga, Y., Cagatay, N. and Meydan, A. F. and PaleoVan Science Team (2013) Seismic evidence of shallow gas from Lake Van, eastern Turkey. Marine and Petroleum Geology, 48 . pp. 341-353. DOI 10.1016/j.marpetgeo.2013.08.017.

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Abstract

Analysis of multi-channel seismic reflection and chirp data from Lake Van (eastern Turkey) reveals various shallow gas indicators including seismic chimneys, enhanced reflections, bright spots, mud volcanoes, pockmarks, and acoustic blanking. The enhanced reflections, suggesting the presence of free gas, are most dominant and observed at more than 200 locations. They are characterized by very-high amplitude reflections and occur in both deep and shallow sedimentary sections. Some enhanced reflections are accompanied by very subtle seafloor expressions such as mounds, which may suggest active venting activity. Seismic chimneys or columnar zones of amplitude blanking have been observed in much of the surveyed area. Seismic chimneys in the study area cannot be associated with any known faults that would act as migration pathways for deep fluids. This suggests that the observed structures in Lake Van sediments allow the preferential emission of gases which might be for a large share of biogenic origin. The acoustic blanking, characterized by transparent or chaotic seismic facies, is seen in the eastern part of the lake. The lakeward edge of the acoustic blanking largely coincides with the 100 m water depth contour, indicating that (past) changes of the hydrostatic pressure may be responsible for the distribution of these anomalies. Mound-like features, interpreted as mud volcanoes, occur in a few locations. The presence of these features may suggest active gas emission. Very strong amplitude anomalies or bright spots with negative polarity, indicating gas-charged zones, are also seen in a number of locations. Pockmarks are observed only in the northeastern part of the study area. The scarce occurrence of pockmarks in the study area might be ascribed to a higher permeability of the lake sediments or to the absence of the substrate/reservoir providing the critical mass of gases necessary to produce such features. Turbidites, tephra layers, and deltaic deposits have the potential to provide ideal conditions to allow the sediments to act as a gas reservoir.

Document Type: Article
Additional Information: WOS:000328095100025
Keywords: Shallow gas; Lake Van; Bright spots; Enhanced reflections; Seismic chimneys; Pockmarks
Research affiliation: Kiel University
OceanRep > GEOMAR > FB4 Dynamics of the Ocean Floor > FB4-GDY Marine Geodynamics
Refereed: Yes
Open Access Journal?: No
DOI etc.: 10.1016/j.marpetgeo.2013.08.017
ISSN: 0264-8172
Projects: PaleoVan, FLOWS
Date Deposited: 03 Jun 2013 08:27
Last Modified: 26 Jul 2017 07:41
URI: http://oceanrep.geomar.de/id/eprint/21350

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