Hydrate Ridge is a 25-km-long, 15-km-wide accretionary ridge located on the continental margin ~80 km west of Newport, Oregon (Fig. F1). A widespread bottom-simulating reflector (BSR), numerous seafloor gas vents, outcrops and subcrops of gas hydrate, authigenic carbonates, and chemosynthetic organisms characterize the area (Tréhu, Bohrmann, Rack, Torres, et al., 2003). During Leg 204, nine sites (1244–1252) were drilled and cored on southern Hydrate Ridge (SHR). From seven of these sites, highlighted in red on Figure F1, we collected the samples reported in this study. Detailed descriptions of the geologic and biologic setting can be found in the Leg 204 Initial Reports volume (Tréhu, Bohrmann, Rack, Torres, et al., 2003) and references therein.