Late Quaternary climate-induced lake level variations in Lake Peten Itza, Guatemala, inferred from seismic stratigraphic analysis

Anselmetti, F. S. and Ariztegui, D. and Hodell, D. A. and Hillesheim, M. B. and Brenner, M. and Gilli, A. and McKenzie, J. A. and Mueller, A. D. (2006) Late Quaternary climate-induced lake level variations in Lake Peten Itza, Guatemala, inferred from seismic stratigraphic analysis. Palaeogeography Palaeoclimatology Palaeoecology, 230 (1-2). pp. 52-69. ISSN 0031-0182

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We used seismic images and sedimentary data from piston cores to conduct a sequence stratigraphic analysis of sediments in Lake Pete´n Itza´, northern Guatemala. Our results document lake level fluctuations in this lowland Neotropical region that were related to glacial-to-interglacial climate change during the Late Pleistocene. A bathymetric survey of Lake Pete´n Itza´ (area=100 km2) revealed a maximum water depth of ~160 m and the existence of a deep cryptodepression that extends 50 m below modern sea level. The great depth suggests that the basin held water even during arid conditions associated with full glacial periods. Lake Pete´n Itza´ may thus possess the only long continuous lacustrine sediment record of Late Pleistocene environmental and climate change in the lowland Neotropics. Two seismic reflection campaigns imaged the subsurface basin sediments that overlie basement. The sediment package was divided into four major seismic sequences (T, G, R, and B). Sequences are separated by unconformities that represent depositional cycles related to lake level fluctuations. Sediments of the uppermost sequence (T) were recovered and radiocarbon-dated in Kullenberg piston cores taken along a water depth transect. Seismic profiles reveal a basin-wide paleoshoreline just below sequence T at ~56 m below present lake level. This constructional feature formed during a lowstand of the last glacial period when the lake was reduced to only ~13% of its present volume. In cores taken landward of the paleoshoreline, Late 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 (t). It marks the base of the uppermost seismic sequence T and is dated in several cores between ~11.1 and 10.2 cal kyr BP. Lake level rose quickly at this time in response to a shift from arid-to-humid climate conditions at the Late Glacial/Early Holocene transition. We infer a similar sediment response to climate variations in the older stratigraphic sequences (G, R, and B), related to earlier glacial-to-interglacial and stadial-to-interstadial cycles. Older sequences are also distinguished from one another by erosional unconformities that probably represent major lake level falls. Future recovery of the older stratigraphic record by drilling in Lake Pete´n Itza´ will provide ages for these older units and enable us to test the depositional model inferred from seismic stratigraphy.

Item Type: Article
Uncontrolled Keywords: NIL AREP
Subjects: 01 - Climate Change and Earth-Ocean Atmosphere Systems
Divisions: 01 - Climate Change and Earth-Ocean Atmosphere Systems
Journal or Publication Title: Palaeogeography Palaeoclimatology Palaeoecology
Volume: 230
Page Range: pp. 52-69
Depositing User: Sarah Humbert
Date Deposited: 16 Feb 2009 13:01
Last Modified: 23 Jul 2013 10:01

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