Geo-Marine Research on the Mediterranean and European-Atlantic Margins, International Conference and TTR-17 Post-Cruise Meeting of the Training-through-Research Programme, Granada, Spain, 2-5 February 2009
Comas, M.; Suzyumov, A.E. (2009). Geo-Marine Research on the Mediterranean and European-Atlantic Margins, International Conference and TTR-17 Post-Cruise Meeting of the Training-through-Research Programme, Granada, Spain, 2-5 February 2009. IOC Workshop Report, 220. UNESCO: Paris. 64 pp.
Deel van: IOC Workshop Report. UNESCO: Paris, meer
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| Trefwoorden |
Hydrocarbons
Seeps
Marien/Kust |
| Abstract |
Introduction to the TTR-17 resultsM. Ivanov1*, N. Kenyon2, M. Comas3, L. Pinheiro4, J.-S. Laberg5 and shipboard Scientific party1UNESCO-MSU Centre for Marine Geology and Geophysics, Faculty of Geology, Moscow StateUniversity, Vorobjevy Gory, Moscow 119899, Russia *(fu@geol.msu.ru)2 Southampton Oceanography Centre, Empress Dock, Southampton, SO14 3ZH, United Kingdom3Instituto Andaluz de Ciencias de la Tierra, C.S.I.C. and University of Granada, CampusFuntenueva, 18002 Granada, Spain4Departamento de Geoci"ncias and CESAM, Universidade de Aveiro, 3800 Aveiro, Portugal5Department of Geology, UniÍersity of Tromsø, N-9037 Tromsø, NorwayThe TTR-17 cruise was subdivided into three Legs. Leg 1 focused on study of sea mounds andhydrocarbon seeps in the West Alboran Sea. The Melilla Sea mounds discovered by Spanishscientists in 2006 (Comas et al., 2007) were studied in detail with high resolution seismic, deep towedsidescan sonar, underwater TV system and sampling. These investigations confirmed the presence oflarge coral buildups comparable by their dimensions to carbonate mud mounds of the PorcupineSeabight. This is the first and very important documentation of large-scale cold water coral reefs in theAlboran basin.Detailed investigations of the Carmen structure (recorded for the first time in the TTR-14 cruise,Kenyon et al., 2006) revealed that this is a relatively small, but extremely active deep water mudvolcano (MV). According to our observations the Carmen MV is the most active one in the entireregion including the Alboran Sea and the Gulf of Cadiz. This fact undoubtedly will attract attention ofmany investigators. The Carmen structure is characterized by a very strong gas emission,predominantly methane. Bubbling of free gas from the sea bottom was observed during underwaterTV runs. Sediment cores from the crater of this mud volcano are presented by very fresh mud volcanicbreccia with a very high gas and water saturation. Free gas bubbling from a large TV-grab sample(about 0,25 m3) continued for no less than 10 minutes and has been recorded on video. It leads us to asuggestion that gas most probably was stored in structure II gas hydrates form which are normallystable in temperature-pressure conditions of the sea bottom at the crater area. After lifting sedimentson the deck of the ship hydrates started rapidly decomposing producing a lot of free gas and water.Abundant chemosynthetic fauna included two types of pogonofora and living chemosynthetic shells.Various methane derived carbonates have been documented and sampled in the Alboran basin for thefirst time.Leg 2 in the Gulf of Cadiz was devoted to studying mud volcanoes, coral settlements, gas hydrateaccumulations and relationships between large mud/salt diapirs (diapiric ridges) and seepagestructures. The crest of a large diapiric body located to the east of the Mercator MV was surveyed withseismic, sidescan sonar, underwater TV, and sampled. The top of this structure is strongly eroded andlately covered by carbonate crusts, coral settlements and partially buried with recent sediments. Agravity core collected from this structure showed increasing pore water salinity with depth similar tothose observed earlier in a crater of the Mercator MV and on some other structures. This fact canprobably characterize this structure as a salt diapir or at least a diapiric structure containing some salt.The same observations were done on the Renard Ridge N-E of the Gemini mud volcano. This suggeststhat a chain of topographic highs including the Don Quichotte MV, the Alfa and Betta mounds, the top(plateau) of the Pen Duick escarpment are just shallow crest position or outcrops of elongated saltdiapiric ridges. In this case such structures as the Fiuza MV, the Gemini MV and a chain of smallseepage structures at the foot of the Pen Duick escarpment were generated due to fluid migration(front) along the southern side of a salt diapiric ridge. Yet another remarkable new discovery on theMoroccan margin during this Leg is an extensive field of cold water coral settlements located alongthe shelf break east of the Mercator and Al Idrisi mud volcanoes. They were mapped firstly in 2002during the TTR-12 cruise (Kenyon et al., 2003) but we were not able to interpret these peculiarfeatures at that time. Now they were mapped with high resolution sidescan sonar, surveyed with a TVcamera, and sampled.One new mud volcano has been discovered in the Portuguese deep water area. A big number ofdifferent kinds of deep water chemosynthetic fauna were collected on the Portuguese margin. One ofthe most exciting events of this part of the cruise was sampling for the first time gas hydrates from thedeepest in this area Porto mud volcano. Most of hydrate samples look very surprising for us, becausethey have been represented by perfect cubic or prismatic crystals semitransparent for the first severalseconds after subsampling; they look very similar to crystals of quartz or calcite.A few last days of Leg 2 were spent on dragging alkaline igneous rocks of the Late Cretaceous agefrom outcrops of the Estremadura Spur area offshore Lisbon. In addition to different kinds of igneousrocks, remnants of huge (probably very old) cold water corals have been collected. These samples mayhave significant interest to specialists studying history of deep water coral distribution in the AtlanticOcean.Leg 3 aimed mainly to studying Cenozoic sandy systems on the Norwegian continental slope andabyssal plain of the Lofoten Basin. Mapping of the modern system, the Andoya Canyon – LofotenBasin Channel with deep towed sidescan sonar started in 2003 (TTR-13). It was continued andaccompanied with very successful sampling. Spectacular records of large recent submarine slides havebeen obtained during this Leg on the Norwegian continental slope as well.Origin of small but numerous positive structures broadly distributed on the Vøring Plateau raised a lotof discussions and open questions in previous years. During this Leg these structures were sampledwith a TV-controlled grab and proved to be thick bacterially induced iron hydroxide crusts andchimneys with sufficient presence of phosphates.ReferencesComas, M.C and Pinheiro, M. L. (2007). Discovery of Carbonate Mounds in the Alboran Sea: TheMelilla Mound Field. 1st International Conference of the Moroccan Association of PetroleumGeologists (MAPG) in association with the American Association of Petroleum Geologists(AAPG), Marrakesh, October 28-31, Abstract Book:73Kenyon et al (Eds.) (2006). Interdisciplinary Geoscience Studies of the Gulf of Cadiz and WesternMediterranean Basins. Preliminary results of investigations during the TTR-14 cruise of RVProfessor Logachev, July-September, 2004. IOC Technical Series No. 70. UNESCO, 115 pp.Kenyon N.H., M.K. Ivanov, A.M. Akhmetzhanov and G.G. Akhmanov (Eds.) (2003).Interdisciplinary Geoscience Research on the North East Atlantic Margin, Mediterranean Sea, andMid Atlantic Ridge During the TTR-12 Cruise of RV Professor Logachev, June–August 2002,IOC Technical Series No. 67, UNESCO, 156 pp |
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