HR: 0800h
AN: PP21A-1543    [Abstracts]
TI: Paleoenvironmental history of the lowland Neotropics from Lake Peten-Itza, Guatemala
AU: * Anselmetti, F S
EM: flavio.anselmetti@erdw.ethz.ch
AF: ETH Zurich, Geological Institute, Zurich, 8092 Switzerland
AU: Hodell, D A
EM: dhodell@geology.ufl.edu
AF: University of Florida, Department of Geological Sciences, Gainesville, FL 32611 United States
AU: Ariztegui, D
EM: daniel.ariztegui@terre.unige.ch
AF: University of Geneva, Institute F.- A. Forel, Versoix, 1290 Switzerland
AU: Brenner, M
EM: brenner@ufl.edu
AF: University of Florida, Department of Geological Sciences, Gainesville, FL 32611 United States
AU: Mueller, A D
EM: andreas.mueller@erdw.ethz.ch
AF: ETH Zurich, Geological Institute, Zurich, 8092 Switzerland
AB: During the last glaciation, all shallow lake basins in the northern lowland Neotropics were dry because of increased aridity and/or lowered sea level; consequently, no long continuous lacustrine records have yet been recovered from this region. Detailed seismic surveys of Lake Peten-Itza in northern Guatemala revealed that this lake is deep (160 m) and possesses a thick (>100 m) stratigraphic record. Its great depth suggests that the basin held water even during arid glacial periods. In fact, seismic profiles show a basin-wide paleoshoreline at ~56 m below present lake level that formed during the last glacial lowstand when the lake was reduced to only ~13 % of its present volume. In piston cores taken landward of the paleoshoreline feature, glacial-age deposits consist of paleosols, indicating subaerial exposure. Basinward of the shoreline, sediments are composed of dense gypsum sands and interbedded silty clays, reflecting authigenic gypsum formation under arid climate conditions. The top of the soil horizon and cessation of gypsum precipitation are represented by a strong seismic reflection that has been dated in several cores at 10.2 cal kyr BP. This transition represents a shift from arid late glacial to moist early Holocene conditions that coincided with the end of the Preboreal Period in Europe. From seismic profiles, we infer a similar sediment response to climate variations in the older stratigraphic sequences. We will recover the older stratigraphic record by drilling in early 2006 (Jan-March). Six primary and four alternative drilling sites have been identified that fall along a depth transect extending from ~30 m to near the deepest point (~150 m) in Lake Peten-Itza. A sequence stratigraphic approach will be employed to constrain the vertical range of past lake level variations for glacial, interstadial, and interglacial stages during the late Pleistocene. Deep-water cores should provide continuous records of paleoclimate and paleoenvironmental change in the northern lowland Neotropics on both orbital and suborbital timescales.
UR: http://plaza.ufl.edu/hodell/
DE: 0935 Seismic methods (3025, 7294)
DE: 1225 Global change from geodesy (1222, 1622, 1630, 1641, 1645, 4556)
DE: 1616 Climate variability (1635, 3305, 3309, 4215, 4513)
DE: 1637 Regional climate change
SC: Paleoceanography and Paleoclimatology [PP]
MN: Fall Meeting 2005