Multidisciplinary study of geological processes on the North East Atlantic andWestern Mediterranean margins. Preliminary results of geological and geophysical investigations during the TTR-9 cruise of R/V Professor Logachev June-July, 1999
Kenyon, N.H.; Ivanov, M.K.; Akhmetzhanov, A.M.; Akhmanov, G.G. (Ed.) (2000). Multidisciplinary study of geological processes on the North East Atlantic andWestern Mediterranean margins. Preliminary results of geological and geophysical investigations during the TTR-9 cruise of R/V Professor Logachev June-July, 1999. Technical Series. Intergovernmental Oceanographic Commission = Série technique, 56. UNESCO: Paris. iv, 102 + annexes pp.
Part of: IOC Technical Series. Intergovernmental Oceanographic Commission = Série technique. UNESCO: Paris. ISSN 0074-1175
A number of topics related to slope processes, tectonics, and diapirism in different locations on the North East Atlantic margin and in the Mediterranean Sea were the focus of investigations conducted during the 9th UNESCO/IOC cruise of RV Professor Logachev.The new seismic data confirmed the presence of a buried slump complex of presumably Plio-Pleistocene age at the central western margin of the Faeroe-Shetland Channel, as was reported from the TTR8 cruise (Kenyon et al., 1999). The acoustic records and core data from Leg 1 of the TTR9 cruise proved that slope instability of the eastern Faeroe margin is more widespread than previously thought.A wide range of mainly longitudinal current induced bedform types has been observed, representative of both low and high bottom current speed. A sandy top seen in all cores also confirms generally enhanced bottom current activity in the area. Further evidence for strong current activity is provided by the very coarse lag deposits found in the area of the steep escarpments in the southern part of the area. Investigations of these lag deposits showed a high percentage of non-basaltic material indicative of a non-Faeroes origin.Studies on the Irish margin of the eastern Rockall Trough showed that the lower slope is dominated by canyon system channels with intervening seabed showing evidence of instability and contourcurrent activity. Moderate currents exist capable of limited seabed erosion in exposed places. The upper slope is subject to a much more rigorous current regime with no discernible preferred direction.The currents have eroded considerable quantities of the silty clay seabed to generate an upper (>c.30cm) layer of sandy gravel with common cobbles and occasional boulders causing a hazard to deployed equipment.The existence of contourite deposits on the deep Portuguese margin west of Porto, one of the primary targets of the study during Leg 2, was not fully confirmed. Potential areas were only recognized north and west of the Vigo Seamount, and in the basin located between the continental slope and the Porto Seamount based on data collected from the 3.5 kHz profiler.Acquisition of additional seismic and sidescan sonar data broaden the existing TTR8 OKEAN long-range sidescan sonar coverage and showed the development of the canyon system basinward. The Setubal canyon was found to be the most active conduit of terrigenous material to the Tagus abyssal plain.Data collected during Leg 2 in the Gulf of Cadiz allowed identification of three regions of mud volcanism and diapirism: Western Moroccan Field (WMF), Middle Moroccan Field (MMF) and Eastern Moroccan Field (EMF). In the MMF, OREtech sidescan sonar data, grab samples and gravity core samples confirm the existence of two mud volcanoes, (Yuma and Ginsburg). Methane hydrates (clathrates) were recovered from Ginsburg. In the EMF, gravity core samples confirm the existence of three mud volcanoes (Kidd, Adamastor, TTR) and seismic and sidescan sonar data suggest that there are at least five more mud volcanoes and four diapiric ridges.One underwater TV line obtained from the northeastern slope of the Gulf showed the character of the seabed within a contour current channel which is an active pathway for basinward sand transport.During Leg 3, surveys in selected sectors of the Alboran and South Balearic basins in the Western Mediterranean Sea, a new mud volcano (Granada) associated with a mud diapir field was discovered on the Moroccan margin of the Alboran Sea.OKEAN imagery obtained on the Balearic basin showed a variety of processes taking place. Basement outcrops, canyon systems and slope instability features were successfully mapped. Samples of hard rocks dredged on some outcrops provided a valuable source of information on the age and origin of the basement in the Alboran and Balearic basins.
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