Fossil sponges from a localized cold-seep limestone in Oligocene rocks of the Olympic Peninsula, Washington

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Abstract
A limited fauna of relatively simple, thin-walled, hexactinellid sponges, including moderately coarse-textured, funnellike Hexactinella(?) conica new species, fine-textured, tubular to branched Hexactinella(?) tubula new species, fragments of delicate Eurete goederti(?) Rigby and Jenkins, 1983, and Farrea(?) species, has been found in the Oligocene Lincoln Creek Formation on Canyon River, in the southcentral part of the Olympic Peninsula, Washington. These sponges dominate a chemosynthetic invertebrate assemblage that included the gastropod Provanna antigua Squires, 1995; the polyplacophoran Leptochiton alveolus (Lovén, 1846), and radiolarians. Most of the sponges are preserved as silica in a localized cherty and botryoidal, calcareous cement-filled limestone formed at bathyal depths by bacterial oxidation of methane at a cold seep. This is the third known report of sponges from ancient chemosynthetic deposits.