HR: 1330h
AN: PP42A-0859    [PDF]
TI: Mapping and Collection of Deep-Sea Corals from Seamounts in the NW Atlantic
AU: * Scheirer, D
EM: Daniel_Scheirer@brown.edu
AF: Brown University Geological Sciences, 324 Brook St. Box 1846, Providence, RI 02912
AU: Adkins, J
AF: Geological and Planetary, MC 100-23 1200 E. California Blvd., Pasadena, ca 91125
AU: Yoerger, D
AF: Dept. of AOPE, WHOI, Woods Hole, MA 02543
AU: Shank, T
AF: Dept. of Biology, WHOI, Woods Hole, MA 02543
AB: We mapped the occurrence of living and fossil deep-sea corals using R/V Atlantis, DSV Alvin, the autonomous vehicle ABE, and a towed camera system, and we collected these corals and their associated fauna at sites on the New England and Muir seamount chains in the northwest Atlantic. On cruise AT7-35 (May-June 2003; the Medusa Expedition), we used a nested mapping approach to span observational scales from tens of kilometers with shipboard multibeam sonar to centimeters with human and camera observations. With these observations, we characterized the volcanic structure of the seamount edifices, their modification by mass-wasting, their primary volcanic surface features, and the deposition of sediments and metal-rich encrustations. These seamount properties, in turn, define the physical habitat important for recruitment and sustenance of faunal communities, and they influence oceanographic factors such as current concentration and stagnation, localized upwelling, and vertical mixing. Manning and Gosnold seamounts, on the New England chain, rise as much as 4 km above the surrounding abyssal plain; they are distinct edifices that merge with adjacent cones near their lower reaches. The largest edifices in the study area have undergone sector collapse, leaving up-slope hanging walls and amphitheaters above landslide run-outs. Visual images of these landslide slopes show sedimented talus with isolated blocks. The Muir seamount chain is composed of a handful of major edifices that merge to form a ridge $>$100 km in length. Sector collapse away from the axis of the ridge has sharpened the ridge and left occasional buttressing ridges perpendicular to the main ridge. Away from the landslides, the seamount tops are generally flat, and the seamount flanks are characterized by down-slope ridges and volcanic knobs. Much of the flat seafloor is completely sedimented; bottom currents have variable intensity and direction based on observed sedimentary structures and submersible handling. Isolated features rise above the flat sediments, and they are generally Mn-encrusted or they exhibit primary lava morphology (pillow and sheet-flow surfaces). On the flanks of the seamounts, the larger knobs are free of sediment. In all cases, exposures of bare rock host more abundant and diverse sessile communities than adjacent sedimented areas. There is a general increase in fossil and modern biomass as depth decreases from ~2500 m to ~1000 m. Abundant corals, collected throughout this depth range, will allow the reconstruction of paleoprofiles of water mass properties in the NW Atlantic since the Last Glacial Maximum, and hopefully several tens of kyr prior.
DE: 3045 Seafloor morphology and bottom photography
DE: 4207 Arctic and Antarctic oceanography
SC: Paleoceanography and Paleoclimatology [PP]
MN: 2003 Fall Meeting