Structural control on fluid and authigenic cement composition of cold seeps in the offshore Santa Barbara Basin: A GIS-based approach EICHHUBL, Peter, GREENE, Gary, MAHER, Norm, and HATCHER, Gerry, Monterey Bay Aquarium Research Institute, 7700 Sandholdt Rd., Moss Landing, CA 95039. To assess the control of faults and anticlines on fluid migration in the Santa Barbara Basin, location and composition of offshore seeps and associated carbonate deposits are being investigated and compared to subsurface fluid compositional and structural data. The project was initiated by extensive bathymetric and sidescan mapping of the Santa Barbara Basin, followed by ground-truthing, shallow sediment coring, rock sampling, and shallow pore water sampling using MBARI's remotely operated submersible ROV Ventana. Widespread active hydrocarbon seepage was found along the northern shelf of the basin and appears to be distributed along anticlinal trends and faults. Active fluid seepage was typically observed as methane release during push coring, as bacterial mats, and as tar extrusions. Past seep activity is evident by authigenic carbonate deposits, mud volcanoes, and extensive tar flows. GIS is an integral part of the project, including layout of ship tracks for multibeam bathymetry and side scan acquisition, planning of ROV dive operations, ROV sample collection, and data interpretation. Real-time GPS tracked the ship and ROV location during ROV dives, allowing immediate correlation of observed seafloor features with features mapped by bathymetry and side scan. Georeferenced cataloguing of fluid and carbonate compositional data allows recognition of spatial trends and correlation of samples with respect to structural and seafloor topographic features such as fault and slump scarps. Geochemical data are superimposed onto structure contour maps of the basin and onto fault outcrop maps derived from sub-bottom profiling. In addition, surface fluid chemical data are being compared to formation water samples from offshore oil production wells, potentially providing indication to the source of seep fluids.