HR: 14:40h
AN: GC53A-07    [Abstracts]
TI: A Holocene Record of Hydrological Fluctuations in the Northern Chilean Altiplano (Lago Chungar\'{a})
AU: * Valero-Garces, B L
EM: blas@ipe.csic.es
AF: IPE-CSIC, Apdo 202, Zaragoza, 50080 Spain
AU: Saez, A
EM: a.saez@ub.edu
AF: University of Barcelona, Marti i Franques s/n, Barcelona, 08028 Spain
AU: Pueyo, J
AF: University of Barcelona, Marti i Franques s/n, Barcelona, 08028 Spain
AU: Taberner, C
AF: IJA-CSIC, Lluis Sole i Sabaris, Barcelona, 08028 Spain
AU: Bao, R
AF: University of A Coruna, Campus da Zapateira s/n, A Coruna, 15071 Spain
AU: Schnurrenberger, D
AF: LRC- U of Mn, 500 Pillsbury Dr SE, Minneapolis, MN 55455 United States
AU: Myrbo, A
AF: LRC- U of Mn, 500 Pillsbury Dr SE, Minneapolis, MN 55455 United States
AU: Shapley, M
AF: LRC- U of Mn, 500 Pillsbury Dr SE, Minneapolis, MN 55455 United States
AU: Herrera, C
AF: Universidad Catolica del Norte, Avda Angamos 0610, Antofagasta, 1280 Chile
AU: Moreno-Caballud, A
AF: IPE-CSIC, Apdo 202, Zaragoza, 50080 Spain
AU: Gonzalez-Samperiz, P
AF: IPE-CSIC, Apdo 202, Zaragoza, 50080 Spain
AU: Giralt, S
AF: IJA-CSIC, Lluis Sole i Sabaris, Barcelona, 08028 Spain
AU: Oriol-Gibert, R
AF: University of Barcelona, Marti i Franques s/n, Barcelona, 08028 Spain
AU: Edwards, L
AF: U of Mn, 220 Pillsbury Hall, Minneapolis, MN 55455 United States
AU: Schwalb, A
AF: Technische Universitat Braunschweig, Pockelsstrase 3, Braunschweig, 38106 Germany
AB: Holocene records of moisture availability in the Central Andes and the Altiplano show contrasting and even opposite signals and time-transgressive millennial-scale climatic changes across the region, particularly between the Titicaca Basin and the Atacama Altiplano. A multiproxy study of a 13 kyr record of Lago Chungar\'{a} (18ø 15' S, 69ø 10' W, 4520 m a.s.l.) provides new data to solve some of the paleoclimate controversies as regional moisture availability patterns during the early and mid Holocene and the onset of modern ENSO conditions. Lago Chungara originated after the emplacement of the Parinacota volcano debris avalanche that blocked the Chungar\'{a} River prior to 13 cal. kyrs ago. A seismic survey and fifteen Kullenberg cores allowed a detailed 3-D reconstruction of the 8 m long sedimentary sequence. The chronological model is based on 5 AMS $^{14}$C on bulk organic matter and 3 U/Th dates on authigenic carbonates and shells. To assess the typically large (and variable) reservoir effect, we dated modern sediments and waters, and constrained the model with time markers based on a $^{210}$Pb age model for the last 150 yrs, volcanic ashes of known age, and the U/Th dates. We performed high-resolution analyses by an X-ray fluorescence core scanner and magnetic, sedimentological, mineralogical, isotopic, and biological (pollen, diatoms and ostracodes) analyses on selected cores. Statistical analyses helped to separate the volcanism from climate as the key driving forces in the hydrological and sedimentological evolution of the lake. Three main lacustrine units are identified on top of the pre Parinacota avalanche substrate. The basal unit (13 - 7.2 cal. kyrs BP) is a finely laminated diatomite. The middle unit (7.2 - 4.5 cal. kyrs BP) is banded and it is composed of diatomites and carbonate-rich layers. The diatomaceous upper unit (after 4.5 cal. kyrs BP) is banded to massive, and it contains abundant volcanic layers (lapilli, ash layers). Increased volcanic activity after 6 cal kyrs BP and climate-driven hydrological changes seem to have been conducive to increase carbonate precipitation during the middle unit. Seismic features of the middle unit in littoral areas evidence an alluvial progradation compatible with lowstand intervals and a subsequent lake level rise episode during the upper unit. The reconstructed hydrological variability in the Lake Chungar\'{a} shows fluctuating lake levels during the Pleistocene-Holocene transition and the early Holocene (13 to 7.2 cal kyrs BP), and the mid Holocene (7.2 - 4.5 cal kyrs BP), and the highest lake levels during the late Holocene. Preliminary frequency analyses in laminated basal unit suggest that ENSO-like variability was also present during the early Holocene in the Altiplano. The presence of mid - Holocene arid intervals supports the regional extent of this period of reduced moisture through the region.
DE: 9360 South America
DE: 9604 Cenozoic
DE: 3344 Paleoclimatology
DE: 1809 Desertification
DE: 1815 Erosion and sedimentation
SC: Global Climate Change [GC]
MN: 2004 AGU Fall Meeting