georefid:2002-035456SEDIS Publication Catalogueana.macario@awi.dehttp://sedis.iodp.org/pub-catalogue/informationpointOfContact2011-06-23T00:00:00Zhttp://sedis.iodp.org/pub-catalogue/index.php?id=2002-035456<gco:CharacterString>Mass wasting, methane venting, and biological communities on the Mendocino transform fault</gco:CharacterString>2002-01-01publicationgeorefid:2002-035456Stakes, Debra S.Monterey Bay Aquarium Research Institute, Moss Landing, CA, United StatesauthorTrehu, Anne M.Oregon State University, United StatesauthorGoffredi, Shana K.authorNaehr, Thomas H.authorDuncan, Robert A.authorGeological Society of America (GSA), Boulder, CO, United StatespublisherdocumentHardcopyGeology (Boulder)30 (5)407-410Chemosynthetic cold-seep vestimentiferan tubeworms and vesicomyid clams inhabiting oceanic basaltic rock have been discovered on the Gorda Escarpment sector of the Mendocino transform fault 73 km west of Cape Mendocino, northern California. The sparse cold-seep animals are "biomarkers" that identify zones of focused fluid venting from a methane gas horizon seismically imaged as a bottom-simulating reflector (BSR) within sediments on the southern flank of the escarpment. This is the first example of a methane-based cold-seep community on exposed oceanic basement rock within an area dominated by transform tectonics. This discovery extends the range of known environments in which the subsurface flow and venting of methane-rich fluids are linked both with geological activity and chemosynthetic communities. Observations by remotely operated vehicle of the distribution of the animals, sediment, basaltic talus, and basement outcrop delineate a large slump headscarp that channels subsurface fluid. Seismic surveys of the southern flank of the Mendocino transform fault (the Vizcaino block) define a BSR hosted in the thick sedimentary sequence that projects to the wall of the Gorda Escarpment at the same depth as the chemosynthetic community. The well-defined BSR in the marine sediment of the Vizcaino block results from an accumulation of methane gas possibly capped by methane hydrate. The isotopic composition of Mg-calcite found along the headscarp (delta (super 13) C = -65 ppm; delta (super 18) O = 4.8 ppm) is consistent with fluids derived from dissociated methane hydrate. We propose that the tectonic uplift along this transform margin has resulted in the lateral, northward movement of methane from the Vizcaino sedimentary sequence to the east-trending wall of the north-facing Gorda Escarpment.completedOceanographyEnvironmental geologyaliphatic hydrocarbonsalkanesbacteriabathymetrybiomarkersbottom-simulating reflectorsC-13/C-12CaliforniaCape Mendocinocarboncarbonate rockschemosynthesiscold seepscommunitiescontinental margindeep-sea environmentEast Pacificecologyfaultsgas hydratesgas seepsgeochemistrygeophysical methodsgeophysical profilesgeophysical surveysGorda RiseHumboldt County CaliforniahydrocarbonsInvertebrataisotope ratiosisotopesLeg 167marine environmentmarine sedimentsmass movementsMendocino fracture zonemethanemultichannel methodsNorth PacificNortheast PacificO-18/O-16Ocean Drilling ProgramODP Site 1022organic compoundsoxygenPacific Oceansedimentary rockssedimentsseismic methodsseismic profilesslumpingstable isotopesstrike-slip faultssurveyssymbiosistransform faultsUnited StatesupliftsventsVermesurn:org.iodp:exp:167urnlargerWorkCitationcampaignurn:org.iodp:exp:167:site:1022urnlargerWorkCitationstudyurn:org.iodp:exp:167urnlargerWorkCitationcampaignEnglishgeoscientificInformation-125.2034-125.203440.045140.0451