Abstract

• Main Authors: Anne M. Trehu, Collaborators Marta Torres, Joel Johnson, Chris Goldfinger, Bob Collier (oregon State, Erwin Suess, Katja Heeschen, Dirk Klaeschen (geomar
• Other Authors: The Pennsylvania State University CiteSeerX Archives
• Format: Text
• Language: English
• Subjects: Pinnacle; Methane hydrate
• Online Access: http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.215.7144; http://www.netl.doe.gov/publications/proceedings/02/MethaneHydrate/Trehu_Abstract.pdf

Gas hydrates and free gas, as indicated by the seismic proxy known as the BSR, are widespread on the Oregon continental margin. A number of geological, geochemical and geophysical studies have been conducted here in the past several years in preparation for deep drilling during Leg 204 of the Ocean Drilling Program, scheduled for summer 2002. In this presentation, we first present an overview of the seafloor morphology and reflectivity. We then discuss recent results from samples and measurements made at the seafloor. Finally, we discuss the subsurface plumbing as determined from a recent 3-D seismic survey and objectives of the planned drilling. Hydrate Ridge, known as Second Ridge prior to discovery in 1996 of abundant massive methane hydrate at the seafloor, is a 15-km-long northeast-trending accretionary ridge 80 km west of Newport, OR, that was formed by subduction of the Juan de Fuca plate beneath North America. The northern summit of the ridge is covered by a carapace of authigenic carbonate whereas the southern summit is mostly covered by sediment, with the exception of a single spectacular carbonate pinnacle on the SW flank (Clague et al., 2001; Torres et al., 1999, Johnson and Goldfinger, in prep). This has been interpreted to indicate that the northern summit is at a more mature stage in the evolution of a hydrate-bearing accretionary ridge (Trehu et al., 1999), a