Resumen de Sedimentología y magnetismo de sedimentos ricos en hidratos de gas de "Hydrate Ridge" (margen de Oregón - ODP LEG 204): aplicación en estudios paleoclimáticos
Elena Piñero Melgar, Eulàlia Gràcia i Mont, Juan C. Larrasoaña, Francisca Martínez Ruiz, Gemma Ercilla Zárraga, A. Vizcaino, Miguel Garcés Crespo
During Leg 204 of the Ocean Drilling Program (ODP) in the accretionary complex of the Cascadiasubduction zone, offshore the Oregon margin, more than 3600 meters of sediment cores wereobtained. In order to complete the different analysis made during the Leg, the sedimentological,geochemical and magnetic study of more than 600 samples is being carried on. The sedimentological preliminary results show that the sediment of Hydrate Ridge consists in silty clay to sandy siltsediments, with some foraminifer-bearing zones and some gradded silt layers interpreted as turbi-ditic events. Volcanic glass horizons have been identificated also as turbidite layers. The magneticresults show that two main types of sediments can be distinguished in the Southern Hydrate Ridge:one characterized by high Isothermic Remanent Magnetization (IRM) 0.9 T/k values, correspondingto greigite dominated magnetic assemblages and another characterized by low I RM 0.9 T/k valuestypical for greigite-magnetite mixtures. The first one is located near the surface and below the Bottom Simulation Reflector (BSR), indicating the existence of a fossil Gas Hydrate Stability Zone(GHSZ). The comparison between sedimentological, mineralógicaI, magnetic and geochemical results will allow to better understand the gas hydrates formation, migration and location, and willhelp to identificate other fossil BSRs.
