Plattform Platform	Reise-Nr. Cruise-No.	Zeitraum Period	Projekt Project	Arbeitsgebiet Working area
Maria S. Merian	MSM20-2	17.01.2012 - 15.02.2012		South Atlantic Ocean

Fahrtleiter Chief Scientist	Institut Institute	Auslaufhafen Port of departure	Einlaufhafen Port of return	Stationskarte Station map	Schiffsroute Trackchart
Jegen-Kulcsar Marion	Helmholtz Centre for Ocean Research Kiel (GEOMAR)	Walvis Bay	Recife

Ziel der Reise / Objectives of Cruise:

MSM 20/2 According to classical plume theory, the Tristan da Cunha hotspot is thought to have played a major role in the rifting of the South Atlantic margins and the creation of the aseismic Walvis Ridge by impinging at the base of the continental lithosphere shortly before or during the breakup of the South Atlantic margins. However, Tristan da Cunha is enigmatic as it cannot be clearly identified as a hot-spot but may also be classified as a more shallow type of anomaly that may actually have been caused by the opening of the South Atlantic. The equivocal character of Tristan is largely due to lack of geophysical data in this region. It is of central importance to characterize the region around Tristan da Cunha with geophysical data in a more coherent way to understand the tectonic processes of the opening of the South Atlantic and the formation of the Walvis Ridge, i.e. to understand whether Tristan da Cunha is the cause or the consequence of the rifting. We, therefore, staged a multi-disciplinary geophysical study of the region by acquiring passive marine electromagnetic and seismic data, bathymetric data as well as gravity data from which we will derive an electrical resistivity, velocity and density model down to a depth of several hundred kilometers. These models will be interepreted in the context of geochemical data and tectonic models developed within the SPP1375 �South Atlantiv Margin Processes and Links with onshore Evolution (SAMPLE). On the cruise MSM 20-2 we acquired bathymetric and gravity data within the Tristan region and deployed 26 OBMT and 24 OBS as well as two seismic and one MT land stations on the neighbouring uninhabited Nightingale island for a year long data acquisition. The lands tations are on loan from the German geophysical instrumentation pool at the Geoforschungszentrum Potsdam. The recovery of the stations is planned for January/February 2013 during a second Merian Cruise (Capetown 28.1.2013 to Walvis Bay 22.2.2013). The cruise also offered the opportunity to invite two Geologists from GFZ/TU Berlin for a 5 day rock sampling excursion Tristan.

Messungen / Measurements