--> Abstract: Faunal Communities Associated with Gas and Fluid Seepage in the Sea of Okhotsk, by S. V. Galkin and H. Sahling; #90920 (1999).

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GALKIN, SERGEY V., Institute of Oceanology, Moscow; and HEIKO SAHLING, GEOMAR Research Center, Kiel

Abstract: Faunal Communities Associated with Gas and Fluid Seepage in the Sea of Okhotsk

Since 1986 chemoautotrophic communities have been known from seafloor observations at gas seepage sites off Paramushir Island in the Sea of Okhotsk and sporadically dredged single Vesicomyid clams indicated venting in the Derugin Basin. During the 28th cruise of the R/V Lavrentyev, we discovered a variety of communities based on chemosynthesis along the eastern margin off Sakhalin and in the Derugin Basin.

As shown by hydroacoustic anomalies in the water column and by bottom photographs obtained through a towed video system, seepage appears widespread along the shelf and slope off Sakhalin. Here every single vent location nourishes faunal assemblages dominated either by Thyasirid (Conchocele sp.) or Vesicomyid bivalves. Solemyid bivalves, pogonophora and probably bacterial mats also occur. The different demands on nutrition, based on methane, sulfur and suspension feeding for Conchocele sp. and sulfur oxidation for Vesicomyids, may reflect the geochemical variability of these vent settings.

In the Derugin Basin, at least 4 different species of Vesicomyidae occur between large barite chimney. In a gravity core we observed at least 5 layers of Calyptogena shells dating back at least 26,000 years. Here we document the species composition of the vent sites (based on trawl samples), their distribution (based on video observations) and the geochemical setting (based on core samples) of the newly discovered fluid and gas seepage areas.

AAPG Search and Discovery Article #90920©1999 AAPG Pacific Section Meeting, Monterey, California