Sediment- und Krustenstruktur des Filchner-Ronne-Schelfs, Antarktis

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Herter, U. (2012): Sediment- und Krustenstruktur des Filchner-Ronne-Schelfs, Antarktis , Diplom thesis, KIT, Geophysikalisches Institut Karlsruhe.
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During the austral summer 1994/95 reasonable ice conditions allowed to gather new high quality refraction seismic data parallel to the Filchner-Ronne Ice Shelf (FRS), Antarctica. The data has now been analyzed in detail and a 2D P-wave velocity model has been calculated. For the two profiles in total 12 RefTek stations each with nine geophone chains were placed on the ice shelf and 3175 shots on 480 km were fired by two 32 l BOLT-Airguns. Signals were recorded up to distances of 180 km. Due to the ice coverage it was not possible to shoot straight lines without gaps, which caused some difficulties in the modelling process and lowered the achieved accuracy of the valocity model. Nevertheless this is the best refraction seismic data from the FRS and helps understanding the geodynamic development of the southern Weddell Sea region. The data were modeled using rayinvr and compared to data from older experiments of the AWI and the Soviet Antarctic Experiments. Mostly this shows a good consistency. A main feature of the recording stations in the central shelf area are a lot of interfering signals at distances, where mantle phases are expected. Based on the velocities a density model was derived and fitted to the existing ship- and airborne gravity data. For an integrated interpretation the seismic and gravity data were correlated with magnetic data. The models show a sedimentary basin with a thickness up to 12 km and a large velocity inversion in the lower sediments. The crustal thickness varies from 40 km beneath the Antarctic Peninsula and 14 km without the sediments in the center part of the profile. East of Berkner Island the crustal thickness increases again to about 40 km. The lower crust features velocities between 6.6 and 7.3 km/s. So the data documents the transition from normal to a highly stretched but still not oceanic crust. This is supported by magnetic data that shows very weak anomalies which are not older than M19/20 and can be correlated to velocity highs in the lower crust. So the model supports an interpretation of the Ronne- Filchner Shelf as a failed rift that formed during Gondwana break up.

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