HR: 0830h
AN: PP11A-0215    [PDF]
TI: Orbital and Sub-orbital Periodicities in East Greenland Ice-rafting Since 630 ka
AU: * St. John, K
EM: stjohnke@appstate.edu
AF: Department of Geology, Appalachian State University, Boone, NC 28608 United States
AU: Richie, J
EM: richiejt@appstate.edu
AF: Department of Mathematical Sciences, Appalachian State University, Boone, NC 28608 United States
AU: Flower, B
EM: bflower@seas.marine.usf.edu
AF: College of Marine Sciences, University of South Florida, St. Petersburg, FL 33701 United States
AU: Krissek, L
EM: krissek@mps.ohio-state.edu
AF: Department of Geological Sciences, Ohio State University, Columbus, OH 43210 United States
AB: The presence of hematite-stained ice-rafted debris (IRD) in the Irminger Basin reflects the discharge of debris-laden icebergs from the east central coast of Greenland and possibly Svalbard. In a comprehensive paleoceanographic study of a 630-kyr Irminger Basin sediment record recovered from ODP site 919, it was found that typically 20-40 percent of all the lithic (non-volcanic) grains of the coarse sand fraction were hematite-stained. Modern values for this area do not exceed 15 percent hematite-stained grains, and nearly all modern values greater than 15 percent are in the Greenland-Iceland Sea. This indicates that the modern discharge of icebergs from northern redbed regions to the Irminger Sea is anomalously low, compared to conditions during the last 630 kyr. Spectral and cross-spectral analyses of the site 919 sediment accumulation record were performed using the SPECTRUM program. Statistical results include recognition of 123, 91, 19 and 8-kyr dominant periodicities in the abundance record of hematite-stained IRD. These results indicate that both orbital and sub-orbital forces influenced east Greenland ice-rafting since 630 ka. The 19-kyr period of hematite-stained IRD accumulation lags the 19-kyr period in the Site 919 oxygen isotope record by 3.2 kyr (+/- 1.6 kyr), suggesting that there was a persistent delay in the response of east Greenland ice sheets to changing global climates in the Pleistocene. In addition, the presence of the 8-kyr period suggests that Heinrich-type events may have been a characteristic feature not only of the last glacial cycle but of the Pleistocene in general.
DE: 1635 Oceans (4203)
DE: 3022 Marine sediments--processes and transport
DE: 4267 Paleoceanography
DE: 4863 Sedimentation
SC: Paleoceanography and Paleoclimatology [PP]
MN: 2003 Fall Meeting