COLD SEEPS IN THE SONORA MARGIN BASIN AT GUAYMAS BASIN, GULF OF CALIFORNIA, MEXICO

The Guaymas Basin is a tectonically active zone, as part of the Gulf of California Transtensional System, which accommodates the accretion of new oceanic crust along an overlapping center with two long grabens at its sides, referred as: Northern Rift and Southern Rift. The NE end of the Northern Rift is intercept by the SE segment of the Guaymas Transform Fault which has a deep pull-apart basin parallel to the Sonora Margin. There are many studies on the hydrothermal activity within the rift basins, because of its biological and magmatic process taking place there, although there has been few studies on the nature of cold seeps within the Sonora Margin Basin. On 2010, a research cruise, BIG10, on board the research vessel N/O L'ATALANTE imaged several continuous plumes of bubbles in the water column within the Sonora Margin Basin. The images of these cold seeps at the Sonora Margin were recorded with the EM122 multi-beam echo-sounder on board the N/O L'ATALANT, and are used to locate and characterize some of their physical parameters. These images are correlated within the multi-beam bathymetry map that was gathered using the EM300 multi-beam echo-sounder during the research cruise, GUAYRIV10, on board the B/O EL PUMA on 2010. Also 16 high-resolution seismic profiles across the basin were recorded with the TOPAS PS18 sub-bottom profiler on board the B/O EL PUMA. These profiles are used to define the seismic stratigraphy in the basin and their relation with the cold seeps founded in the Sonora margin. 31,895 water column images were captured on the echo sounder display, at every 6 seconds, at cruising speeds between 3 and 5 knts. Only 6 cold seeps were observed that their plume heights are greater than 600 m from the seafloor. Most of these seeps occur on a structure like a ridge, part of the eastern escarpment of the Guaymas Fault. Geochemical analysis of water samples on the water column collected during GUAYRIV10 near a plume indicates that the water comes from the continent.