HR: 1340h
AN: PP33A-1552    [Abstracts]
TI: Glacial and Interglacial Climate Cycles From a Varved Record (Core MD02-2515) in the Guaymas Basin (Gulf of California)
AU: * Thurow, J
EM: j.thurow@ucl.ac.uk
AF: Earth Sciences, Univ College London, Gower Street, London, WC1E 6BT United Kingdom
AU: Brumsack, H
EM: brumsack@icbm.de
AF: ICBM, Oldenburg University, PO Box 2503, Oldenburg, 26111 Germany
AU: Cheshire, H
EM: h.cheshire@ucl.ac.uk
AF: Earth Sciences, Univ College London, Gower Street, London, WC1E 6BT United Kingdom
AU: Clayton, T
EM: tc1@noc.soton.ac.uk
AF: School of Ocean and Earth Sciences, Univ Southampton, National Oceanography Centre, Southampton, SO14 3ZH United Kingdom
AU: Ganeshram, R
EM: raja.ganeshram@glg.ed.ac.uk
AF: School of GeoSciences, Univ Edinburgh, Grant Institute, West Mains Road, Edinburg, EH9 3JW United Kingdom
AU: Nederbragt, A
EM: a.nederbragt@ucl.ac.uk
AF: Earth Sciences, Univ College London, Gower Street, London, WC1E 6BT United Kingdom
AU: Pearce, R
EM: rp1@noc.soton.ac.uk
AF: School of Ocean and Earth Sciences, Univ Southampton, National Oceanography Centre, Southampton, SO14 3ZH United Kingdom
AB: To test for interaction between long and short climate cycles it is necessary to reconstruct records of interannual to decadal variability over sufficiently long time periods. Marine varved sediments, like Core MD02-2515, are one of the few archives with the necessary resolution. The latest Quaternary in MD02-2515 is predominantly varved with few bioturbated intervals. The Guaymas Basin allows reconstruction not only of regional upwelling and precipitation but also of ocean circulation in the North Pacific (intermediate water) and equatorial Pacific (subsurface water). The material is therefore ideally suited to test for interaction between all scales of climate variability, from orbital scales (glacial/interglacial) via millennial (D/O cycles) to interannual oscillations (ENSO). A varve age model has been compiled, allowing estimation of biogenic and lithogenic fluxes at annual to near annual resolution. The 65 m that were recovered represent the time interval from 7 to 38 kyr BP, with annual accumulation rates ranging from 1.2 mm during the Holocene to 2-3 mm during the last glacial. First results are further based on analysis of nitrogen isotopes, XRF scanning data, and XRF, XRD, TOC, biogenic opal and carbonate analysis of discrete samples. Millennial scale cycles are recorded in nitrogen isotopes and provide a framework for correlation with the Greenland ice-cores. Opal and TOC content are highest in the Holocene, but their annual accumulation rates are two to three times higher during the glacial. XRD analyses of the <2 micron clay fraction and XRF analyses show high lithogenic fluxes during the glacial accompanied by an increase of riverine transport. We therefore conclude that both productivity (upwelling intensity) and lithogenic fluxes (precipitation) were enhanced during the last glacial, suggesting intensification of seasonal contrasts.
DE: 4900 PALEOCEANOGRAPHY (0473, 3344)
DE: 4926 Glacial
DE: 4936 Interglacial
DE: 4960 Stadial
DE: 4964 Upwelling (4279)
SC: Paleoceanography and Paleoclimatology [PP]
MN: Fall Meeting 2005