Geological processes in the Mediterranean and Black Seas and North East Atlantic. Preliminary results of investigations during the TTR-11 cruise of RV Professor Logachov July-September, 2001
Kenyon, N.H.; Ivanov, M.K.; Akhmetzhanov, A.M.; Akhmanov, G.G. (Ed.) (2002). Geological processes in the Mediterranean and Black Seas and North East Atlantic. Preliminary results of investigations during the TTR-11 cruise of RV Professor Logachov July-September, 2001. Technical Series. Intergovernmental Oceanographic Commission = Série technique, 62. UNESCO: Paris. iv, 89 + annexes pp.
Part of: IOC Technical Series. Intergovernmental Oceanographic Commission = Série technique. UNESCO: Paris. ISSN 0074-1175
The research programme of the 11th Training-through-Research Cruise encompassed a broad range of scientific problems, which were studied at locations in the Black and Mediterranean Seas, the Gulf of Cadiz and in the North- Eastern Atlantic. The major topics were: fluid escape related processes (Black Sea, Gulf of Cadiz), recent tectonic and sedimentary processes related to active faults (Aegean Sea), slope instability (Ebro margin), sand transport and deposition processes in the deep-sea (Gulf of Cadiz), formation of polimetalic crusts and nodules (Madeira Seamounts).Gas hydrates were recovered for the first time in the Northwestern part of the Black Sea in the area without mud volcanoes and at a water depth of 900 m. Most of the fluid escape features were observed along faults suggesting that the latter are important conduits for the upwards migration of fluids. Numerous sediment failures and buried debris flows found in the study area indicate that a large portion of the slope was prone to failure in the near past. The sediment failures can be related to fluid escape structures and/or to gas hydrate dissociation events.New seismic and high resolution sidescan sonar data provided new insights on the morphology and internal structure of hitherto poorly studied mud volcanoes in the Central Black Sea. It was suggested that various morphologies of mud volcano edifices might be characteristic of different stages of their evolution.New seismic records were obtained across Kazakov and NIOZ mud volcanoes in the Sorokin Trough (Northeastern Black Sea). Kazakov mud volcano has deeper roots which lie below the penetration of the seismic system used and were not observed on the records. NIOZ mud volcano crowns a large diapir seen on the seismic image.An area of complex interaction between growing clay diapirs and bypassing turbidity currents was observed during high resolution deep-towed sidescan sonar survey. Some of the mud volcanoes showed evidence of recent activity. Gas hydrates and carbonate crusts recovered from many of them suggest that seepage of fluids enriched in hydrocarbons takes place at the present time.Clear evidence for strike-slip faulting were found within the North Aegean Trough (Mediterranean Sea). Prominent fault scarps were imaged bounding the north and south sides of the North Aegean basin with significant vertical displacement in excess of 700 m.A large landslide occupying more than 2200 km2 was mapped in detail with the deep-towed MAK system on the Ebro margin (Mediterranean Sea). Two surveys provided high resolution visualization of a slide scar and a blocky debris flow, initially recognized on the EM12 multibeam echosounder bathymetry and reflectivity maps. New data suggest that the sliding occurred as a series of events, closely spaced in time, rather than as a single event. Underwater TV surveying showed that the slide is draped by a relatively thick hemipelagic veneer suggesting the lack of recent activity.Detailed investigation of the Iberico High and surrounding diapiric ridges in the Gulf of Cadiz showed that carbonate chimneys are widespread in the area and form large fields on the tops and slopes of the outcropping diapiric structures. Their presence probably reflects the fact of intensive fluid escape from the sediments involved in the diapiric process. Most of the chimneys were seen to have fallen, suggesting that the chimney’s formation took place in the past and that at the present time their growth is negligible or has ceased.A new, conically-shaped mud volcano, named Aveiro, was mapped in detail with the 30 kHz MAK system and sampled in the Portuguese sector of the Gulf. The importance of channelised sand transport was recognised after an analysis of sidescan and high resolution seismic data obtained by a 100 kHz deep-towed MAK-1M survey across a sandy depositional lobe formed by gravity flows at the termination of the Gil Eanes contourite channel.Several fields of ferromanganese crusts were identified on underwater TV footage obtained on the slopes of Unnamed and Unicorn seamounts in the vicinity of the Madeira Island. An extensive collection of ferromanganese crust was retrieved from Unnamed Seamount slopes with the TV guided grab and kept for further laboratory analyses.
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