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.

Interpretation of new multichannel seismic reflection profiles indicates that the Palomares margin was formed by crustal-scale extension and coeval magmatic accretion during middle to late Miocene opening of the Algero-Balearic basin. The margin formed at the transition between thinned continental crust intruded by arc volcanism and back-arc oceanic crust. Deformation produced during the later positive inversion of the margin offshore and onshore is partitioned between~N50°E striking reverse faults and associated folds like the Sierra Cabrera and Abubacer anticlines and N10-20°E sinistral strike-slip faults like Palomares and Terreros faults. Parametric subbottom profiles and multibeam bathymetry offshore, structural analysis, available GPS geodetic displacement data, and earthquake focal mechanisms jointly indicate that tectonic inversion of the Palomares margin is currently active. The Palomares margin shows a structural pattern comparable to the north Maghrebian margins where Africa-Eurasia plate convergence is accommodated by NE-SW reverse faults, NNW-SSE sinistral faults, and WNW-ESE dextral ones. Contractive structures at this margin contribute to the general inversion of the Western Mediterranean since~7 Ma, coeval to inversion at the Algerian margin. Shortening at the Alboran ridge and Al-Idrisi faults occurred later, since 5 Ma, indicating a westward propagation of the compressional inversion of the Western Mediterranean.

In this study, detailed mapping of the 'Messinian markers' and examination of their geometrical relationships in the SW Valencia trough (Western Mediterranean) have revealed the style and depositional processes associated with emersion of continental margins during the Messinian Salinity Crisis (MSC). Based on multichannel seismic profiles and well data, this article evidences the existence of two Messinian depositional units in intermediate basins (Complex Unit and Upper Unit) and four main Messinian erosional surfaces (Margin Erosion Surface, Bottom Surface, Top (Erosion) Surface and Intermediate Surface). Results show that (1) initial rapid sea-level drawdown and exposure of the shelf and upper slope of the Valencia margin induced large-scale destabilization of the continental slope and deposition of large detrital bodies at the base-of-slope in the form of major mass-transport deposits (MTD); (2) as sea level continued to drop, the development of the Margin Erosion Surface attained full development on the margins and eroded the clastic units (MTDs) deposited during initial drawdown. At the same time, a submarine drainage network formed in the deepwater Valencia trough; (3) persistent lowstand and restrictive conditions in the area resulted in deposition of the evaporites that form the Upper Unit in the SW Valencia trough.