HR: 13:40h
AN: OS22C-01    [PDF]
TI: Late Quaternary History of the Northeast Pacific Ocean off Vancouver Island, Canada
AU: * McKay, J L
EM: mckay.jennifer@uqam.ca
AF: GEOTOP, University of Quebec at Montreal, C.P. 8888, succursale Centre-Ville, Montreal, QC H3C 3P8 Canada
AU: Pedersen, T
EM: tfp@uvic.ca
AF: School of Earth and Ocean Sciences, University of Victoria, Petch Building 168, 3800 Finnerty Road, Victoria, BC V8P 5C2 Canada
AB: Data for marine sediment cores collected from the continental margin off Western Canada indicate that dramatic changes in productivity and oxygen minimum zone intensity occurred during the last 16 kyr B.P. During the late glacial marine organic matter accumulation in sediments was greatly reduced off Vancouver Island. This reflected low primary and export production because glacial-mode atmospheric circulation (i.e., the dominance of the Aleutian Low) did not drive upwelling in the region. At start of the Bolling warm period (14.3 kyr B.P.), and coincident with the retreat of glaciers from the continental shelf, there was a substantial increase in the burial of organic matter. Much of this organic material was old terrestrial organic matter derived from the erosion of shelf sediments. However, the accumulation of marine organic matter also increased in the Bolling and peaked in the Allerod (13.5 to 12.6 kyr B.P.). At this time the marine organic carbon accumulation rate was an order of magnitude higher than in the late glacial and Holocene. Other paleoproductivity proxies (i.e., bio-barium, opal and alkenone abundances) also indicate increased marine productivity during the Allerod. Since productivity in the region is controlled by the upwelling of nutrient-rich subsurface waters the data suggest enhanced upwelling, which is also alluded to by radiocarbon data (i.e., a decrease in benthic-planktonic age differences). Redox-sensitive trace metal and benthic foraminifera data suggest that the intensity (i.e., degree of oxygen-depletion) of the oxygen minimum zone (OMZ) also fluctuated during the deglacial. Notably, there is a prominent increase in OMZ intensity during the Allerod. The corresponding increase in marine organic carbon accumulation at this time and lack of any evidence of decreased ventilation suggests that OMZ intensification was a response to increased primary productivity and carbon export. Intensification of the OMZ during the deglacial is documented along the length of the entire California Current System, but it appears to have been delayed by approximately 1500 years off Vancouver Island.
DE: 4267 Paleoceanography
DE: 4825 Geochemistry
DE: 4870 Stable isotopes
DE: 4875 Trace elements
SC: Ocean Sciences [OS]
MN: 2003 Fall Meeting