HR: 15:30h
AN: OS53B-07    [Abstracts]
TI: Geophysical Surveys in the Southern Gulf of Mexico - Preliminary Results from R/V Meteor Cruise M67/2
AU: * Spiess, V
EM: vspiess@uni-bremen.de
AF: Bremen University, Klagenfurter Strasse, Bremen, 28219, Germany
AU: Ding, F
AF: Bremen University, Klagenfurter Strasse, Bremen, 28219, Germany
AU: Bruening, M
AF: Bremen University, Klagenfurter Strasse, Bremen, 28219, Germany
AU: Fekete, N
AF: Bremen University, Klagenfurter Strasse, Bremen, 28219, Germany
AU: Keil, H
AF: Bremen University, Klagenfurter Strasse, Bremen, 28219, Germany
AU: Bohrmann, G
AF: Bremen University, Klagenfurter Strasse, Bremen, 28219, Germany
AB: In March/April 2006, R/V Meteor Cruise M67/2 was carried out in the southern Gulf of Mexico to study fluid and gas seepage in shallow sediments and in particular to investigate the occurrences of asphalts on the sea floor. The working program included both geophysical survey work on regional and local scale as well as geologic and geophysical station work. Among the geophysical methods, high resolution multichannel seismics, sediment echosounding, swath bathymetry, deep tow side scan sonar and water column acoustic profiling were used. Main objectives were to study the origin of asphalt ‘volcanism' and the nature and extent of fluid/gas seepage systems on the sea floor and in the water column. Multichannel seismic surveys were ranging in water depth from ~1000 m in the South to more than 3500 m in the North, covering areas of pronounced salt tectonics, rafting and diapirism. The surveys were targeted to investigate the sub-seafloor structures above oil slicks on the sea surface, which were likely locations of pronounced fluid seepage. They reveal a larger number of bright spots at shallow sub-bottom depth, which have probably mostly developed as a result of salt diapirism and associated fault deformation. From North to South, the degree of diapirsm and deformation increases and topography changes from more circular hills (knolls) to diapiric ridges, revealed by a complete swath bathymetric chart. Stratigraphic analyses of sediment echosounder and high resolution seismic data can be further used to identify the onset of deformation, which is imaged in variations of sediment thickness, derived from mostly turbiditic sediment input, as a result of uplift. The new parametric sediment echosounder system Parasound (Atlas Hydrographics) was also used to image the water column in the vicinity of Chapopote Knoll during bathymetric surveys and ROV and station work. A dense grid of survey lines revealed clear evidence for gas bubbles in the water column, originating from a spot near the asphalt occurrences.
DE: 3004 Gas and hydrate systems
DE: 3025 Marine seismics (0935, 7294)
SC: Ocean Sciences [OS]
MN: 2007 Joint Assembly