Taphonomic Signature of Petroleum Seep Assemblages on the Louisiana Upper Continental Slope: Recognition of Autochthonous Shell Beds in the Fossil Record

Chemoautotrophically-based benthic communities on the Louisiana continental slope are currently producing the only significant localized, autochthonous shell accumulation in the northern Gulf of Mexico shelf and slope region. These sites are well below storm wave base and are not subject to anthropogenic disturbance. Five distinctive biofacies are associated with petroleum seepage, dominated respectively by vestimentiferan tubeworms, lucinid, thyasirid and vesicomyid clams and mytilid mussels. The taphonomy of petroleum seeps includes dissolution as the most pervasive mode of shell alteration throughout all the biofacies