HR: 1330h
AN: PP22A-1196    [PDF]
TI: Neotropical Climate Change Related to Intertropical Convergence Zone Migration During the Last Deglaciation
AU: * Hillesheim, M B
EM: mbhilles@ufl.edu
AF: Department of Geological Sciences, University of Florida, 241 Williamson Hall, Gainesville, FL 32611 United States
AU: Hodell, D A
EM: dhodell@geology.ufl.edu
AF: Department of Geological Sciences, University of Florida, 241 Williamson Hall, Gainesville, FL 32611 United States
AU: Curtis, J H
EM: curtisj@ufl.edu
AF: Department of Geological Sciences, University of Florida, 241 Williamson Hall, Gainesville, FL 32611 United States
AU: Brenner, M
EM: brenner@ufl.edu
AF: Department of Geological Sciences, University of Florida, 241 Williamson Hall, Gainesville, FL 32611 United States
AU: Guilderson, T P
EM: tguilderson@llnl.gov
AF: Center fo Accelerator Mass Spectrometry, Lawrence Livermore National Laboratory, 7000 East Ave L-397, Livermore, CA 94550 United States
AU: Gallup, C
EM: cgallup@d.umn.edu
AF: Large Lakes Observatory, University of Minnesota-Duluth, 10 University Drive, Duluth, MN 55812 United States
AU: Schnurrenberger, D W
EM: schno005@tc.umn.edu
AF: Limnological Research Center, University of Minnesota-Twin Cities, 310 Pillsbury Dr. SE, Minneapolis, MN 55455 United States
AU: Anselmetti, F S
EM: flavio@erdw.ethz.ch
AF: Geological Institute, Swiss Federal Institute of Technology ETH, Sonneggstrasse 5, Zurich, 8092 Switzerland
AU: Ariztegui, D
EM: daniel.ariztegui@terre.unige.ch
AF: Institut Forel and Dept. of Geology, University of Geneva, 10, Route de Suisse, Geneva, 1290 Switzerland
AU: Rosenmeier, M F
EM: mrosenme@pitt.edu
AF: Department of Geology and Planetary Science, University of Pittsburgh, 200 SRCC Building 4107 O'Hara Street, Pittsburgh, PA 15260 United States
AU: Buck, D G
EM: dgbuck@ufl.edu
AF: Department of Geological Sciences, University of Florida, 241 Williamson Hall, Gainesville, FL 32611 United States
AB: The transition from the arid last glacial maximum to the moist Holocene represented a profound change in the Neotropics compared to the relatively small amplitude of climate variablity during the past 10 kyrs. Few lacustrine records of the last delgaciation exist from Central America because most shallow lakes were dry during the last glacial period. Lake Peten-Itza, Guatemala, is the largest (100 km$^{2}$) and deepest (160 m) lake anywhere in the Neotropics. Paleoshorelines observed in seismic surveys document lake level lowering to 58 m below modern level during the Last Glacial Maximum (LGM) indicating that Peten-Itza did not completely dry during this period. Climate in the Peten (17$deg$ N) is influenced by the same seasonal variations in Trade Wind intensity and precipitation, associated with the migration of the intertropical convergence zone (ITCZ) and Azores-Bermuda high-pressure system that affect the Cariaco Basin off northern Venezuela (11$\deg$ N). Thus a similar climate record is expected between Lake Peten-Itza and the Cariaco Basin. For these reasons, Peten-Itza is an attractive target for paleoclimatic study that may provide additional information on past ITCZ behavior during the last glacial-to-interglacial cycle. In May 2002, sediment cores were retrieved from the deep basin of Lake Peten-Itza with some cores extending back to the last delgaciation. We analyszed physical properties, stable isotopes, elemental geochemistry, and mineralogy across Termination I. Glacial-aged sediment in deep cores ($>$50 m) are composed of gypsum sands with high 18O values of bulk carbonate. In shallow cores, the last glacial is represented by a soil horizon indicating subaerial deposition. At the Pleistocene/Holocene boundary, Peten-Itza began to fill rapidly in response to increased precipitation expressed as a 4\permil decrease in $\delta^{18}$O and a mineralogic shift from gypsum to aragonitic and calcareous silty-clays. However, the transition from glacial to interglacial climate was not smooth and considerable structure exists in density, magnetic susceptibility, sediment color, $\delta^{18}$O, sulfur content, and percent carbonate signals. The Younger-Dryas is marked by enriched, $\delta^{18}$O that remain high until the onset of the Holocene "thermal maximum". Density, percent carbonate, and sulfur content were highly variable and may indicate short-term changes in moisture availability. The "8.2 ka event" is expressed as a $>1\permil$ increase in $\delta^{18}$O concurrent with increases in density, susceptibility, and carbonate content as well as a distinct color change in lithology. Sediment color and density in the Peten-Itza core are well correlated with the Cariaco Basin titanium signal, indicating that both records respond to past changes in latitudinal migration of the ITCZ.
DE: 3344 Paleoclimatology
DE: 4215 Climate and interannual variability (3309)
DE: 4825 Geochemistry
DE: 4870 Stable isotopes
DE: 9345 Large bodies of water (e.g., lakes and inland seas)
SC: Paleoceanography and Paleoclimatology [PP]
MN: 2003 Fall Meeting