Report and preliminary results of SONNE cruise SO175, Miami - Bremerhaven, 12.11 - 30.12.2003 : (GAP, Gibraltar Arc Processes)

Kopf, Achim, Bannert, Bernhard, Brückmann, Warner, Dorschel, Boris, Foubert, Anneleen T. G., Grevemeyer, Ingo, Gutscher, Marc-André, Hebbeln, Dierk, Heesemann, Bernd, Hensen, Christian, Kaul, Norbert Emanuel, Lutz, Marco, Magalhaes, Victor Hugo da Silva, Marquardt, Matthias Jonathan, Marti, Alexis V., Nass, Kristin Sabrina, Neubert, Nadja, Niemann, Helge, Nuzzo, Marianne, Poort, Jeffrey Pepijn Dylan, Rosiak, Uwe Dieter, Sahling, Heiko, Schneider von Deimling, Jens, Somoza Losada, Luis, Thiebot, Emanuelle and Wilkop, Thomas Peter (2004) Report and preliminary results of SONNE cruise SO175, Miami - Bremerhaven, 12.11 - 30.12.2003 : (GAP, Gibraltar Arc Processes) Berichte aus dem Fachbereich Geowissenschaften der Universität Bremen, 228 . UNSPECIFIED, Bremen.

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Expedition SO175 using FS Sonne aimed for a multidisciplinerary geoscientific approach with an international group of researchers. Methods covered the entire span from geophysical data acquisition (seafloor mapping, echography, seismic reflection), sediment coring at sites of active fluid venting, in situ heat flow measurements across the entire length of the Gibraltar thrust wedge, the deformation front, landslide bodies, and mud volcanoes, and finally the deployment of a long-term pore pressure probe. Video-supported operations helped to identify fluid vent sites, regions with tectonic activity, and other attractive high priority targets. Qualitative and quantitative examinations took place on board and are continued on land with respect to pore pressure variation, geomicrobiology, sediment- and fluid mobilization, geochemical processes, faunal assemblages (e.g. cold water corals), and gas hydrates (flammable methane-ice-crystals). Main focus of the expedition has been a better understanding of interaction between dynamic processes in a seismically active region region with slow plate convergence.

In the context of earthquake nucleation and subduction zone processes, the SO175 research programme had a variety of goals, such as:
• To test the frictional behaviour of the abyssal plain sediments.
• To explore the temperature field of the 1755 thrust earthquake event via heat flow measurements.
• To assess the role of fluid venting and gas hydrate processes control slope stability and mud volcanic activity along the Iberian continental margin.
• To measure isotope geochemistry of pore waters and carbonates of deep fluids.
• To quantify microbial activity in Gibraltar wedge sediments.
• To test whether microseismicity in the area corresponds to in situ pore pressure changes.
• To find out if enhanced heat flow max be indicative of active subduction.

Initial tentative results during the cruise suggest that there is a component of active thrusting at the base of the wedge, as attested by heat flow data. Based on mostly geochemical evidence, mud volcanism was found less active than previously assumed. Highlights from post-cruise research include the successful deployment of the long-term station and high frictional resistance of all incoming sediment on the three abyssal plains.

Document Type: Report (Cruise Report)
Additional Information: Förderkennzeichen BMBF 01G0175A - 03G0175A Print-Ausg. in der GEOMAR-Bibliothek / Print ed. in GEOMAR Library: X 5 (228)
Keywords: Gulf of Cadiz; seismicity and active faulting; mud volcanism; diapirism; carbonate mounds; cold water corals; microbial AOM; earthquakes; landslides; slope failure; tectonics; evaporites; sediment wedge; gas hydrate processes; oceanography; saline, warm Mediterranean outflow water (MOW)
Research affiliation: OceanRep > GEOMAR > FB2 Marine Biogeochemistry > FB2-MG Marine Geosystems
OceanRep > GEOMAR > FB4 Dynamics of the Ocean Floor > FB4-GDY Marine Geodynamics
ISSN: 0931-0800
Projects: GAP, Gibraltar Arc Processes
Date Deposited: 22 Feb 2013 10:25
Last Modified: 26 Feb 2013 17:20

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