| Summary: | Palaeogene and Neogene fossiliferous carbonates from Barbados, Trinidad and northern Venezuela are interpreted to have formed at ancient cold seep sites. The hydrocarbon seepage that fuelled these chemosymbiotic ecosystems was related to tectonic activity in the southern Caribbean region, particularly the subduction of the Caribbean Plate beneath the North Atlantic Plate. The carbonates and fossils from the Scotland District, north-eastern Barbados, are Eocene–Miocene in age and are associated with two distinct tectonic units: the Sub-Oceanic Fault Zone and a diapiric mélange. The Sub-Oceanic Fault Zone is the tectonic junction between accretionary prism sediments and over-lying thrust sheets of fore-arc basin sediments. The loading of the thrust sheets caused methane-rich fluids to be expelled from the accretionary prism sediments and channelled to the sea floor via the Sub-Oceanic Fault Zone, where it supported chemosymbiotic invertebrate communities containing vesicomyid, lucinid, thyasirid, solemyid and nuculanid bivalves, a variety of gastropods and possibly vestimentiferan tube worms. The diapiric mélange is considered to represent sediment that failed under pressure in the accretionary prism and was remobilised as a diapir that extruded onto the sea floor, providing a conduit for methane and other hydrocarbons that sustained a chemosynthesis-based community of vesicomyid, lucinid and nuculanid bivalves and various gastropods. The geological setting of fossiliferous carbonates known as Freeman's Bay Limestone, in southwest Trinidad, has been less fully investigated. The Freeman's Bay Limestone is a member of the Miocene Lengua Formation, which is believed to have formed in a fore-deep basin on-lapping onto an accretionary prism formed by the subduction of proto-Caribbean crust beneath the South American Plate. The carbonates and fossils of the FBL, including the bivalves Pleurophopsis unioides Van Winkle, 1919 and Thyasira adoccasa Van Winkle, 1919, lucinids, nuculanids and bathymodiolins, and provannid ...
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