Plattform Platform	Reise-Nr. Cruise-No.	Zeitraum Period	Projekt Project	Arbeitsgebiet Working area
Poseidon	429	22.03.2012 - 06.04.2012		Mediterranean Sea Ligure Sea

Fahrtleiter Chief Scientist	Institut Institute	Auslaufhafen Port of departure	Einlaufhafen Port of return	Stationskarte Station map	Schiffsroute Trackchart
Kopf Achim	Universitat Bremen, Zentrum fur Marine Umweltwissenschaften	Heraklion	La Seyne

Ziel der Reise / Objectives of Cruise:

The expedition P429 MEDFLUIDS is associated with three earlier RV Poseidon cruises, i.e. P336 in the Cretan Sea (Kopf et al., 2006), P386 in the Ligurian Sea (Kopf et al., 2009) and P410 on the Mediterranean Ridge accretionary complex (Kopf et al., 2012). The earlier work as well a steh P429 objectives have in common that they investigate complex geodynamic settings with rapid sedimentary processes (mud volcanism, landslides) and fluid flow processes (mud volcanoes, deep-seated faults, groundwater seeps). Objectives included: - Study slope stability in the Cretan Sea north of Crete with complementary gravity coring and geotechnical in situ measurements; - Recover long-term flowmeter instruments from mud volcanoes in the Hellenic Subduction Zone (deployed during cruise P410) and get additional samples and in situ data; and - Recover an osmo-driven long-term insztrument and carry out additional sampling and in situ measurements at the Nice Airport landslide. Among the methods utilised during Poseidon Leg P429 were multibeam site surveys to complement existing bathymetric charts, in situ measurements to characterise the natural state of the materials near the backstop, seafloor sampling, and recovery of long-term instruments to study sedimentological and geochemical phenomena. In the Cretan Sea, off NW Crete, a profile from the Spatha Ridge shelf to an adjacent salt dome was studied. Geophysical data suggest slumping and sliding of sediment, partly as coherent blocks, takes place in an eastward direction. Gravity cores and CPTu measurements support this interpretation and attested that the slide plane material is water-rich. In the landward Mediterrnean Ridge accretionary prism and its backstop, the Inner Ridge, all 5 flowmeters deployed 12 months ago during cruise P410 were successfully recovered. Additional in situ temperature measurements confirm the elevated gradients observed at Milano MV a year ago (exceeding 1000?C/km in places). By comparison, Napoli MV shows signifiantly lower values, indicating lesser activity at present. Further north, three gravity cores sampled material from the contact between Inner Ridge and Cretan margin. The lithologies show eveidence for grey (likely deep-seated) mud and intense sediment deformation. Mass wasting deposits are found regularly in those cores, spanning from debrites with angular clasts of various composition to turbidites. Offshore Nice, gravity coring and CPTu deployments aimed at reconnaissance and recovery of whoel round core for laboratory experiments. Cores were not opened and described. An osmo-sampler in the 1979 landslide scar was recovered and equipped with new pumps and tubings for another year of operation. Scuba divers assisted the seafloor operations.

Messungen / Measurements