HR: 15:25h
AN: U12A-06    [PDF]
TI: Twelve Years of Results from ODP Subseafloor "CORK" Hydrogeological Observatories
AU: * Becker, K
EM: kbecker@rsmas.miami.edu
AF: University of Miami - RSMAS, 4600 Rickenbacker Causeway, Miami, FL 33149 United States
AU: Davis, E E
EM: EDavis@NRCan.gc.ca
AF: Pacific Geoscience Centre, Geological Survey of Canada P.O. Box 6000, Sidney, BC V8L 4B2 Canada
AB: The CORK ("Circulation Obviation Retrofit Kit") sealed-hole observatory was developed 12 years ago by ODP engineers and scientists to investigate in-situ hydrogeological state and processes, through long-term measurements of in-situ temperatures and pressures and sampling of in-situ fluids. CORK capabilities have been expanded recently to allow monitoring and sampling in multiple isolated horizons. To date, 18 CORK hydrological observatory sites have been established in ridge crest, ridge flank, and accretionary prism settings. Observations at these sites have provided precise constraints on the primary driving forces for, and thermal consequences of, sub-seafloor fluid flow caused by thermal buoyancy and tectonic consolidation. Deep in accretionary prisms, high formation pressures have been observed, confirming that plate boundary faults possess little strength. In young ocean crustal settings, surprisingly low lateral temperature and pressure gradients have been documented, implying that the extrusive upper oceanic crust permits efficient transport of fluid, heat, and solutes over distances of many kilometers. CORK observations have also revealed pressure variations and associated fluid flow resulting from co-seismic plate deformation and from tidal, oceanographic, and barometric loading of the seafloor. The characteristics of the formation response to seafloor loading provide constraints on formation elastic and hydrological properties, and allow quantitative estimates of crustal strain to be made from pressure transients related to tectonic events. Strain events have been observed up to 250 km away from several seismic dislocations along subduction, transform, and seafloor spreading plate boundaries.
DE: 0915 Downhole methods
DE: 1894 Instruments and techniques
DE: 3015 Heat flow (benthic) and hydrothermal processes
DE: 5114 Permeability and porosity
DE: 8045 Role of fluids
SC: U
MN: 2003 Fall Meeting