Sedimentary fabrics in the authigenic carbonates from Bush Hill: implication for seabed fluid flow and its dynamic signature

Abstract Seep carbonates, the product of cold seep fluids mediated by microbial activity, archive information on seabed fluid flow and microbiological processes that led to their formation. Sedimentary fabrics are well developed in the authigenic carbonate from active seep sites at Bush Hill, Green Canyon Block 185 of the Gulf of Mexico. This authigenic carbonate has much lower carbon isotope values than typical marine cements and the carbonate is concluded to be derived from the oxidation of seeping petroleum. The authigenic fabrics commonly exhibit microbial or texturally unique sedimentary structures; e.g. framboidal pyrite, clotted microfabric and peloid, botryoidal aragonite, microfilament, and rosette‐like aragonite are all preserved in seep carbonate. These fabrics are indicators of biological influence during microbial oxidation of petroleum and sulfate reduction when cold fluids seep on to the seabed. The textures are therefore considered as additional evidence that can be used to identify and interpret ancient cold‐fluid seeps on seafloor. The difficulty of the preservation of these biogenic fabrics is thought to be related to the redox condition and dynamic signature (e.g. rate of fluid flow) of cold seeps.