One of my major research projects during 2007-2008 has been a study of the Trinity-Tiger shoal complex on the shelf opposite Marsh Island along the central Louisiana coast. During the 2007 field season a comprehensive high resolution seismic, side-scan sonar, magnetometer, and bathymetric survey of the shoals was conducted. Results of this survey determined the sites of vibracores taken this fall (2008) in order to “calibrate” the acoustic data sets to types of shoal sediments and the nature of key subsurface reflectors. The associated picture show a vibracore being collected from the RV Coastal Profiler. The cores will be analyzed in our recent sediments lab using a GeoTek multisensor core logger, a digital photographic scanner, X-ray radiography, and new grain size instrumentation. Graduate student Clint Edrington will use these data sets as the foundation of his PhD research.
Another noteworthy project deals with understanding fluid-gas expulsion on the deep Louisiana continental slope and the chemosynthetic communities that inhabit these sites. The manned submersible DSV Alvin and ROV Jason were used in the first two years of this four year project to collect data at selected sites. The computer-enhanced multibeam bathymetry image of the northern Gulf’s continental slope has the key project sites plotted on it. Site selection was determined by analyzing 3D-seismic data archived at MMS in New Orleans. Surface amplitude anomalies, identified by assessing the strength of the first return (seafloor) on 3D-seismic data, have been found to nearly always represent hydrocarbon seep sites. In conjunction with MMS geologists, I was in charge of site-selection for the project and geological analysis of each site. In addition to analyzing geophysical data, I am investigating characteristics of the authigenic carbonates that form in situ at each site as a by-product of microbial utilization of hydrocarbons that have been migrated from the deep subsurface to the ocean bottom. These interesting deep water carbonates have been collected from shallow slope to deep slope locations. Post-doc Dong Feng from the Chinese Academy of Sciences at Guangzhou is spending two years with me to help work on these carbonates. Researchers from LSU, Penn State, Harvard, University of Georgia, Texas A&M, MMS, NOAA, USGS, and several European universities have been a part of this four year study. Results are extending our understanding of chemosynthetic communities and their sites of occurrence to the full depth range of the northern Gulf of Mexico continental slope.
