Discovery of massive sea floor gas seepage along the Wagner Fault, northern Gulf of California

Abstract

Large-scale gas seepage and fluid ejection features are described from the edges of the active pull-apart Wagner and Consag basins (northern Gulf of California, Mexico), at water depths between 65 and 150 m. Gas vents, pockmarks, possible mud volcanoes, pyrite- and barite-rich sediments, slabs of lithified shell debris, and chemosynthetic fauna were found. Gas venting occurs mainly through N-S synsedimentary small-scale faults and fault-propagation folds that are believed to derive from the Wagner Fault. The presumed mud volcanoes are sub-rounded, domed bathymetric features, several hundreds of metres across, underlain by gas-charged sediments and surrounded by gas vents. Upward gas migration throughout the thick sedimentary sequence produces the fluid expulsion features on the sea floor.