HR: 1340h
AN: PP13B-1488    [Abstracts]
TI: Stable Isotope and Lithologic Variations on the Eirik Drift During the Holocene: Implications for Climate and Deepwater Interactions
AU: * Henderson, S S
EM: samhend@eden.rutgers.edu
AF: Rutgers University, 610 Taylor Rd, Piscataway, NJ 08854 United States
AU: Wright, J D
EM: jdwright@rci.rutgers.edu
AF: Rutgers University, 610 Taylor Rd, Piscataway, NJ 08854 United States
AU: Manley, P L
EM: manley@middlebury.edu
AF: Middlebury College, 427 McCardell Bicentennial Hall, Middlebury, VT 05753 United States
AU: Mountain, G S
EM: gmtn@rci.rutgers.edu
AF: Rutgers University, 610 Taylor Rd, Piscataway, NJ 08854 United States
AU: Miller, K G
EM: kgm@rci.rutgers.edu
AF: Rutgers University, 610 Taylor Rd, Piscataway, NJ 08854 United States
AB: The cyclonic flow of NADW around the southern tip of Greenland and into the Labrador Sea results in the deposition of huge volumes of sediments that form the Eirik Drift. This region is important because it is ideally situated to monitor variations in surface water hydrography and deepwater formation and circulation. It is also proximal to the Greenland ice sheet, which records large and rapid climate variations that may be mirrored in the high-resolution record of proxy indicators within Eirik Drift. Core 21GGC was collected on Cruise KN166-14 on the distal end of Eirik Drift, recovering 4.7 m of silty clays from a water depth of 3472 m. A suite of lithologic (grainsize, %CaCO₃, %SiO₂) and stable isotopic measurements was obtained every 1 to 2cm. The 3.5 kHz profiles, planktonic foraminiferal δ¹⁸O measurements and shipboard magnetic susceptibility (MS) record indicate that the entire core is of Holocene age. In lieu of AMS ¹⁴C dates, which are not yet available, we estimate the bottom of the core to be between 8 and 9 ka in age by correlating the MS record with nearby, well-dated cores. Thus, sedimentation rates are >50 cm/kyr during the Holocene. The mean sortable silt (SS) record shows a general trend of increasing grainsize from the 20 to 28 μm upcore, implying a strengthening of the deep current throughout the Holocene. Superimposed on this trend are five cycles with amplitudes of ~5 μm. If verified, these cycles may reflect the 1500-year cyclicity proposed by other researchers. Similarly, %CaCO₃ measurements increase upcore from 7 to 44%. To account for the large increase in %CaCO₃, we propose that coccolithiphorid productivity, and hence accumulation of CaCO₃, increased at the start of the Holocene. North Atlantic Deep Water (NADW) during the early Holocene entrained primarily terrigenous material of glacial age and deposited it on the Eirik Drift. As CaCO₃ accumulation continued during the Holocene, its relative contribution to the sediment load increased resulting in higher %CaCO₃ values on Eirik Drift. Five higher-frequency cycles in %CaCO₃ may reflect the imprint of climate on the surface water hydrography.
DE: 4900 PALEOCEANOGRAPHY (0473, 3344)
DE: 4962 Thermohaline
SC: Paleoceanography and Paleoclimatology [PP]
MN: Fall Meeting 2005