HR: 0800h
AN: PP21C-1589    [Abstracts]
TI: Preliminary Results from IODP Expedition 307, Porcupine Basin Carbonate Mounds
AU: * Williams, T
EM: trevor@ldeo.columbia.edu
AF: Lamont-Doherty Earth Observatory, 61 Route 9W, Palisades, NY 10964 United States
AU: Kano, A
EM: kano@geol.sci.hiroshima-u.ac.jp
AF: Hiroshima University, Department of Earth and Planetary Systems Science, Graduate School of Science, Higashi-Hiroshima, 739-8526 Japan
AU: Ferdelman, T
EM: tferdelm@mpi-bremen.de
AF: Max-Planck-Institute for Marine Microbiology, Celsiusstr. 1, Bremen, D-28359 Germany
AU: Henriet, J
EM: jeanpierre.henriet@ugent.be
AF: Ghent University, Renard Centre of Marine Geology, Department of Geology and Soil Science, Gent, B-9000 Belgium
AU: Shipboard Scientific Party, I
EM: trevor@ldeo.columbia.edu
AF: IODP, 1000 Discovery Drive, College Station, TX 77845 United States
AB: IODP Expedition 307 (April 26 - May 16, 2005) drilled three sites at Challenger Mound in the Porcupine Seabight, west of Ireland. Deep-water carbonate mounds up to 2 km wide and 200 m high have been found in typical water depths of 500-1000 m along the continental slope of NW Europe from Morocco to Norway. During the last ten years they have been studied using seismics, shallow coring, high resolution bathymetry, and remotely operated vehicles. The partly-buried Challenger Mound is the first to be completely cored to the mound base, with the aim of answering basic questions such as: What is the sedimentology and structure of the mound? What triggered mound initiation? How does the ecosystem interact with sedimentary fluxes to make the mound grow? How are mound growth phases related to glacial-interglacial cycles? What role do microbial communities and geochemical reaction play in the mound? Analytical work is at an early stage, but already shipboard results reveal some of the mound's secrets. The mound body consists of a 155-m-thick sequence of cold-water coral-bearing Pleistocene sediments (floatstone, rudstone, and wackestone), characterized by 10-meter-scale alternation of light gray and dark green intervals. The carbonate-rich and light-colored layers are partially lithified and feature poor coral preservation or even dissolution. The mound base, virtually identical in the on-mound and off-mound holes, is a sharp Pliocene erosional unconformity, separating coral-bearing sediments from a glauconitic and partly sandy siltstone. No evidence was found for a relation between mound development and hydrocarbon seepage. The results from Challenger Mound will help provide a depositional model with which to interpret deep water carbonate mounds in the geological rock record, and we look forward to future drilling of contrasting carbonate mounds.
UR: http://iodp.tamu.edu/scienceops/expeditions/exp307.html
DE: 3022 Marine sediments: processes and transport
DE: 3036 Ocean drilling
DE: 4219 Continental shelf and slope processes (3002)
DE: 4840 Microbiology and microbial ecology (0465)
DE: 4916 Corals (4220)
SC: Paleoceanography and Paleoclimatology [PP]
MN: Fall Meeting 2005