TOPO-MED - Plate re-organization in the Western Mediterranean: lithospheric causes and topographic consequences - Cruise No. MSM15/5 - July 17-July 29, 2010 - Valletta (Malta)-Warnemünde (Germany) (English)

The evolution of the Gulf of Cadiz and the Western Mediterranean Sea is inherently governed by (i) plate convergence between Nubia (Africa) / Eurasia and (ii) subduction related slab-roll back in the Miocene. Both processes are responsible for topographic features forming the Gulf of Cadiz / Gibraltar Arc / Alboran Sea / Rif / Betic domain and deep-seated features related to the consumption of African lithosphere. The cruise MSM15/5 is part of the ESFEUROCORES program TOPO-EUROPE and is aiming to study the interrelation between convergence and major tectonic fault zones in the Gulf of Cadiz and the Alboran Sea and Miocene subduction / deep-seated seismicity at 40-150 km depth. The transit of MARIA S. MERIAN back to Germany served to recover a seismic monitoring network of ocean bottom seismometers (OBS) that was installed in January 2010 in the Gulf of Cadiz during R/V POSEIDON cruise P393, providing a six month long time series of local earthquake data collected on ocean bottom stations. First results suggest that a number of faults visible in swath-mapping bathymetric data remained inactive during the period of monitoring. Detected earthquakes occurred in a band paralleling the Iberian coastline. Most interesting, earthquakes occurred in the mantle, a feature rarely observed in continental lithosphere. Fault mechanisms suggest that earthquakes are caused by the convergence between Africa and Europe. Further, in a piggyback project foraminifera were sampled from the shallow water column in the Mediterranean and Gulf of Cadiz.