HR: 14:25h
AN: OS22C-04    [PDF]
TI: Regime Shifts in Productivity off Baja California During the Late Pleistocene?
AU: * Ortiz, J D
EM: jortiz@kent.edu
AF: Department of Geology, Kent State University, Kent, OH 44242 United States
AU: O'Connell, S E
EM: soconnell@wesleyan.edu
AF: Department of Earth and Environmental Sciences, Wesleyan University, Middletown, CT 06459 United States
AU: DelViscio, J
EM: jdelviscio@cspinet.org
AF: Center for Science in the Public Interest, 1875 Connecticut Ave. N.W.,Suite 300, Washington, DC 20009 United States
AU: van Geen, A
EM: avangeen@ldeo.columbia.edu
AF: Lamont-Doherty Earth Observatory, Columbia University, Palisades, NY 10964 United States
AU: Beaufort, L
EM: beaufort@cerege.fr
AF: CNRS - CEREGE, Univ. Aix-Marseille III Technopole de l' Arbois - BP 80, Aix-en-Provence, 13545 France
AB: The eastern subtropical Pacific is a region of the surface ocean influenced strongly by ENSO but characterized by generally low sedimentation rates. Core MD02-2508 raised from ~700m depth on the Magdelana Margin near the southern tip of Baja California during the IMAGES VIII MONA cruise exhibits high sedimentation rates and appears to extend beyond 100 ka based on a preliminary age model. Work on a piston core collected during a prior cruise to the same location (MV99-PC08) demonstrates a clear correlation between the GISP-2 d18O record, and sedimentary records of diffuse spectral reflectance, organic carbon, calcium carbonate, and benthic foraminifers per gram sediment during the past 52 kyrs. Peaks in organic carbon content, which occur during warm interstadial events, correspond to maxima in benthic foraminiferal absolute abundance that are as much as two order of magnitude greater than those observed during cool stadial events. Although the age model of the core MD02-2508 is preliminary, data from this new core appears to extend this correlation back beyond 100 ka. From 2400 cm to 0 cm, sediment in core MD02-2508, is only laminated during the strongest of the interstadial events and exhibits an inverse linear correlation between calcium carbonate content and organic carbon content. Sediment deposited below 2400 cm are radically different. The base of core MD02-2508 is more distinctly and continuously laminated, exhibiting greater variance in organic carbon and calcium carbonate content. Of perhaps greater significance, there is a positive, exponential relationship between calcium carbonate and organic carbon content off Baja California during this interval, except for brief periods of lower organic carbon and calcium carbonate that exhibit the negative correlation which dominates at the site from 2400-0 cm. These results suggest greatly enhanced marine productivity prior to 100 ka off Baja California than at any time in the past 100 kyrs. One potential way to explain this result is to invoke stronger La Nina-like conditions in response to the enhanced northern hemisphere solar forcing at that time.
DE: 1600 GLOBAL CHANGE (New category)
DE: 3344 Paleoclimatology
DE: 4267 Paleoceanography
DE: 4522 El Ni¤o
SC: Ocean Sciences [OS]
MN: 2003 Fall Meeting