Bohrmann, Gerhard, Linke, Peter, Suess, Erwin and Pfannkuche, Olaf, eds. (2000) RV SONNE CRUISE REPORT SO143 - TECFLUX - I - 1999 : TECTONICALLY-INDUCED MATERIAL FLUXES, HONOLULU - ASTORIA - SAN DIEGO, JUNE 29 - SEPTEMBER 6 , 1999 ; Leg S0143-1a: Honolulu - Astoria June 29 - July 12, 1999, Leg S0143-1b: Astoria - Astoria July 14 - July 30, 1999 Leg S0143-2: Astoria - Astoria July 31 - August 25, 1999, Leg S0143-3: Astoria - San Diego August 26 - September 6 , 1999. . GEOMAR-Report, 093 . GEOMAR Forschungszentrum für Marine Geowissenschaften, Kiel, 248 pp. DOI 10.3289/GEOMAR_REP_93_2000.

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Abstract

The TECFLUX program (= TECtonically induced FLUXes) addresses geophysical,
biogeochemical, and hydrographic processes associated with fluid venting from the
Cascadia continental margin, specifically the processes resulting from the methane
hydrate dynamics at Hydrate Ridge. An international group of scientists from
institutions in Germany, the USA, Canada, and Japan (Table 1 and list of Participating
Institutions) established a long-term research program based on the initial discovery
in 1996 of methane hydrate exposures. At this margin site mixed methane-sulfide
hydrates and carbonates form a pavement along the crest of the ridge at water depths
between 600-1000 m. Vent fields from which methane-charged, low-salinity fluids
containing sulfide, ammonia, 4He, and isotopically light C02 escape, are associated
with these exposures. The fluid emissions characterize a newly recognized
mechanism of dewatering at convergent margins. However, the rates of discharge, the
fluctuations and frequency of pulses, as well as the mechanisms responsible for the
modulations of flow are totally unknown. Also immediate and intriguing questions
concerning the composition, depth distribution, interlayering with sediment, and
physical properties of these near-surface gas hydrates were to be addressed during
SO Cruise 143.

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