2. Fluid and Tectonic Deformation in an Active Transform Margin Ivano W. Aiello, Moss Landing Marine Laboratories, Moss Landing 95039 CA Basement Ridges Sedimentary basins (fluid sources) Cross-faults (pathways of fluid migration) San Andreas Fault System (SAFS) Santa Cruz Monterey Paleo-seeps (fluid sinks) Neogene, authigenic carbonates and oil-saturated sandstones exposed in the Monterey Bay coast ranges represent the ‘plumbing systems’ of fossil hydrocarbon seepages. The seep precipitates are characterized by strong asymmetries, and by fluid conduits that parallel the local NE-trending fracture and fault fields. Our reconstructions suggest that cross-faults intersecting offshore strands of the SAFS could have acted as conduits for hydrocarbon-rich fluids from the basin depocenters (sources) to the seep localities (sinks).