Early Cretaceous hydrocarbon seep carbonates from Wollaston Forland, Northeast Greenland

Early Cretaceous hydrocarbon seep carbonates from Wollaston Forland, Northeast Greenland Nakrem, H.A.1, Little, C.T.S.2 & Kelly, S.R.A.3 1 Natural History Museum, University of Oslo, 1172 Blindern, 0318 Oslo, Norway, h.a.nakrem@nhm.uio.no 2 School of Earth and Environment, University of Leeds, Leeds LS2 9JT, UK, earctsl@leeds.ac.uk 3 CASP, West Building, 181a Huntingdon Road, Cambridge CB3 ODH, UK, simon.kelly@casp.cam.ac.uk Methane seeps are discrete sites where fluids rich in methane flow onto the seafloor. First discovered in 1984, they are now known from all the World’s oceans. Methane seeps support highly unusual biological communities where the primary energy source for these ecosystems is not solar, but reduced chemicals, such as methane and hydrogen sulphide. The current project focuses on methane-derived carbonate bodies in the Kuhnpasset Beds, which are Late Barremian (Early Cretaceous) aged silty mudstones, cropping out on Wollaston Forland, Northeast Greenland (Kelly et al. 2000). The Kuhnpasset Beds contain a sparse mollusk fauna whereas the carbonate bodies contain an unusual faunal assembage dominated by large bivalves, including the lucinid Cryptolucina kuhnpassetensis, the modiomorphid Caspiconcha whithami and Solemya. In addition there are ammonites, belemnites, nautiloids, and abundant driftwood, sometimes bored by the bivalve Turnus. Recent field work has revealed that in addition to that published there is a much richer macrofauna, including thyasirid bivalves, scaphopods and a diversity of gastropod species. The carbonate bodies have calcite cemented tube systems, zoned calcite crusts and sparite void fills. The carbonate bodies formed on the seafloor in a mid- to outer shelf situation at the end of a period of extensional rifting on the eastern Greenland passive Atlantic margin. The underlying faults may have acted as migration pathways for methane migration to the seafloor. The source rocks for this methane were probably the underlying Late Jurassic black shales at depths of