Plumes, large igneous province rocks and associated deformation: a geophysical study of Walvis Ridge, offshore Namibia - Cruise No. MSM17/1 - November 23 - December 29, 2010 - Mindelo (Cape Verde) - Walvis Bay (Namibia) (English)

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R/V MARIA S. MERIAN Expedition MSM17/1 investigated the crustal and uppermost mantle structure, and morphology of the Walvis Ridge, offshore Namibia, and southwest Africa. Techniques used were marine wide-angle active seismic, multichannel reflection seismic, ocean bottom magnetotellurics, and high-resolution bathymetric swath mapping. We accomplished deployment and successful recovery of 112 ocean bottom seismometer (OBS) or ocean bottom hydrophone (OBH) stations, and deployed 24 ocean bottom magnetotelluric (OBMT) instruments for longer-term (about one month) data recording. Deployments were on two profiles, one on the middle and lower continental slope on the Namibian passive margin in NNW-SSE direction, and a second one from the Walvis Ridge crest far into the southern Angola Basin in WNW-ESE direction. In addition, air gun shots were fired on two margin-parallel profiles on the upper slope and shelf, to be recorded by a seismological land array deployed in the Kaoko-Veld of northern Namibia. High-resolution bathymetric data were acquired on all profiles. In addition, the northwest slope of Walvis Ridge around the ocean-continent boundary was bathymetrically surveyed, to document landforms likely created by magmatic processes, crustal deformation, and submarine mass wasting. Reflection seismic data were collected on all profiles to investigate the thickness of the sediment cover on the crustal basement. Expedition MSM17/1 terminated at Walvis Bay on 29th December 2010, with all scientific objectives achieved, and zero loss of instrumentation and ship time.