HR: 0800h
AN: PP21C-1588    [Abstracts]
TI: Hi-Res MCS Evidence of Spatial and Temporal Variability in Sedimentation Rates From Pliocene Sediment Buildups on Eirik Drift, SW of Greenland
AU: * Earley, R J
EM: rearley@rci.rutgers.edu
AF: Rutgers University, Department of Geological Sciences, Wright Geological Laboratory, 610 Taylor Road, Piscataway, NJ 08854 United States
AU: Mountain, G S
EM: gmtn@rci.rutgers.edu
AF: Rutgers University, Department of Geological Sciences, Wright Geological Laboratory, 610 Taylor Road, Piscataway, NJ 08854 United States
AU: Wright, J D
EM: jdwright@rci.rutgers.edu
AF: Rutgers University, Department of Geological Sciences, Wright Geological Laboratory, 610 Taylor Road, Piscataway, NJ 08854 United States
AU: Manley, P L
EM: manley@middlebury.edu
AF: Middlebury College, Department of Geology McCardell Bicentennial Hall, Middlebury, VT 05753 United States
AB: Contourite sediment drifts have long been studied as records of deep-sea circulation history and as sites for high resolution proxy data based on core samples. Understanding the origin and development of local features is critical to reliably placing these histories and proxy data into a larger context of sedimentation, ocean circulation and related changes of global climate. During the summer of 2002, we collected a 15 x 35 km grid of high resolution MCS data on Eirik Drift as part of a larger study of current controlled sedimentation in the North Atlantic. We identified four to six buried, quasi-sinusoidal sediment buildups measuring 1.5 to 2 km long and 150 m high in about 2500 m of water on the NW flank of Eirik Drift, 150 km south of the southern tip of Greenland. Ties to ODP Site 646 of Leg 105 and IODP Site 1307 of Leg 303 bracket these buildups to between the middle Early Pliocene and early Late Pliocene. Overlying sediments reveal a profound change in drift-building geometry nearly contemporaneous to both a change in the nannofossil assemblage at Site 1307 and the onset of IRD reported elsewhere in the North Atlantic. The first buildup formed adjacent to a large slide scarp likely to have occurred in the middle Early Pliocene. The crest of each subsequent buildup migrated laterally 250-500 m as it grew. The striking difference between these several bedforms and typical migrating sediment waves is these buildups grew individually and sequentially, not simultaneously as occurs in a more laterally extensive field of sediment waves. Although similar bedforms have not been reported elsewhere, the model we present does not require hydrological or geological characteristics unique to Eirik Drift. We propose that seafloor topography constrains and steers sediment-laden bottom water flowing along a surprisingly narrow path on several hundred thousand year timescales. We suggest this led to isolated buildups on Eirik Drift with as much as 3-fold increases in sedimentation rates over distances of merely 5-10 km. These and other, yet-to-be-detected sediment concentrations provide highly attractive targets for sampling especially high-resolution paleoceanographic records.
DE: 3022 Marine sediments: processes and transport
DE: 3025 Marine seismics (0935, 7294)
DE: 4962 Thermohaline
SC: Paleoceanography and Paleoclimatology [PP]
MN: Fall Meeting 2005