15th Training-through-Research Cruise

ttr 15 map

Interdisciplinary studies of deep-water cold seeps, sedimentary environments and ecosystems were conducted by RV Professor Logachev in the Black and Tyrrhenian Seas and the Gulf of Cadiz during the 15th Training-through-Research Cruise of UNESCO-IOC.

During Legs 1 and 2 TTR-15 investigated active seep sites in the Russian, Georgian and Turkish sectors of the Black Sea. Long-range OKEAN sidescan sonar and deep-towed high-resolution MAK-1M sidescan sonar mapping as well as seismic profiling were used to locate sites of active fluid and gas discharge. Detailed observations by video-guided instruments and ROV investigations were performed prior to seafloor sampling by a gravity corer and a TV-grab. Seeps, where free gas bubbles are escaping from the sea floor, were successfully observed on the Kobuleti Ridge (Georgia), at water depths between 1100 - 850 m, by acoustic anomalies in the water column on raw sonar data and as high backscatter intensity areas. Since free gas should become converted to gas hydrate at depths below 750 m of the Black Sea, the presence of free gas is explained by fast transport from a large gas reservoir below the lower boundary of the gas hydrate stability field in the sediments. Bottom-seismic reflections are well imaged in the area. The seeps on the Kobuleti Ridge (Georgia), as well as on the first anticline of the Tuapse Foldbelt and the Shatsky Ridge, are characterised by carbonate and shallow gas hydrate deposits. At four distinct mound locations, three on the Kobuleti Ridge and one on the Shatsky Ridge, oil and other higher hydrocarbon gases have been detected for the first time, indicating seepage from deeper petroleum reservoirs.

 

During Leg 3 a survey of the northern slope of the Stromboli volcano in the Tyrrhenian Sea continued the work commenced during TTR-14 cruise aimed at collecting more high resolution data for ongoing study of the volcano flank collapses. Results indicate that the thickest, coarse-grained landslide deposit extends over a NNW elongated area at water depths between 1000 and 2000 m at a distance of 6 to 8 km from the shoreline. The deposit consists of several discrete, mainly chaotic assemblages of fresh cobble-sized scoriae and lava flow clasts within a coarse sand matrix. Down-slope and laterally, the coarse-grained deposit grades to black volcaniclastic sand often arranged in ripple bed forms. A turbidity current generated by the event traveled for at least 24 km and was capable of depositing sand on a 200 m high opposite flank of Stromboli Canyon. New sidescan sonar data were acquired from the Angitola slope valley area on the Calabrian margin. They were integrated with already available multibeam bathymetry and show that the valley is composed of three tracts with different gradient, planform, cross section and sedimentary processes. 30 kHz sidescan sonar coverage of the Cefalu basin located on the Sicilian margin revealed a widespread sediment instability affecting channel-levee complexes, which dominates the slope settings in the area.

 

During Leg 4, three main areas were investigated in the Gulf of Cadiz: (1) the Moroccan Mud Volcano Field; (2) the Deep Portuguese Mud Volcano Field; (3) a submarine canyon system in the northwest Portuguese sector. High resolution sidescan sonar, underwater video and bottom sampling data enabled the detailed characterization of several previously know mud volcanoes and associated cold seeps and ecosystems on the Moroccan Margin. Four (4) mud volcanoes were discovered in the deepwater part of the Portuguese margin. Their location seems to be controlled by major very deep strike-slip faults. A sunken 200-meter long cargo vessel that transported anthracite (presumably during the 1st World War) was discovered on the bottom of the Gulf of Cadiz and investigated with a deep towed  video camera. The underwater camera run across the head of the Cadiz submarine valley investigated the changes in the local ecosystems related to the presence of the Mediterranean Outflow Water. The study also highlighted the significant level of pollution in the axial part of the canyon system with various types of man-made objects (e.g. bottles, tins, plastic bags etc.).

 


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              cruise report
post-cruise meeting abstracts