Gashydrate in europäischen Meeresgebieten Größte Vorkommen im Schwarzen Meer und im europäischen Nordmeer 22.11.2019/Kiel. Erdgas, gespeichert in sogenannten Gashydraten, findet man weltweit an vielen Kontinentalrändern. Im Rahmen des von der Europäischen Kommission geförderten Projektes MIGRATE (Marine Gas Hydrates: An Indigenous Resource of Natural Gas for Europe) wurde nun erstmalig eine Bestandsaufnahme der Vorkommen in europäischen Meeresgebieten zusammengetragen. Teilergebnisse des vom GEOMAR Helmholtz-Zentrum für Ozeanforschung Kiel koordinierten Projektes wurden jetzt in der internationalen Fachzeitschrift Marine and Petroleum Geology veröffentlicht.
This study analyses pockmark morphology and their spatial distribution in Isfjorden relative to seabed morphology, bedrock geology, fault systems, glacial landforms and processes using multibeam bathymetric data. It provides insight into the possible mechanisms of pockmark formation, high density pockmark field evolution, and fluid migration pathways. A total of 1304 pockmarks occur in the Isfjorden at water depths of 40 to 320 m, varying from circular to elongate in plan-view. Their diameter ranges from 14 to 265 m and their depths from 1 to 11 m. Elongate pockmarks are dominant in the Isfjordbanken and outer Isfjorden where the seafloor is influenced by the West Spitsbergen Current. The West Spitsbergen fold-and-thrust belt and other fault systems subcropping at the Isfjorden seafloor correlate spatially with the high density pockmark zones. The pockmarks are preferentially located on the marine sediments draping the bedrock of Isfjorden fjord system. They are most abundant in the areas underlain by Jurassic-Cretaceous and the Triassic-Lower Jurassic bedrock. Pockmarks found ahead of submarine slope failures may have formed due to dewatering of soft sediments as a result of rapid increase of overpressure caused by deposition of glacigenic debris lobes. Fault conduits, potential source rock and thin postglacial sediment layers are found to be crucial for the formation of pockmarks. Modeling results of the near-shore subsea permafrost and potential gas hydrate stability zone imply thawing permafrost and gas hydrate dissociation as additional possible mechanisms for pockmark formation in Isfjorden.
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