HR: 0800h
AN: GC51C-1064    [Abstracts]
TI: Sedimentary Iron Oxyhydroxides Fluxes in Lago Cardiel (Argentina): Estimating Late Holocene Wind Intensity in Southernmost Patagonia
AU: * Ariztegui, D
EM: daniel.ariztegui@terre.unige.ch
AF: University of Geneva, Dept. of Geology and Paleontology, 13 rue des Maraichers, Geneva, 1205 Switzerland
AU: Waldmann, N
EM: nicolas.waldmann@terre.unige.ch
AF: University of Geneva, Dept. of Geology and Paleontology, 13 rue des Maraichers, Geneva, 1205 Switzerland
AU: Gilli, A
EM: agilli@geology.ufl.edu
AF: ETH, Geologisches Institut - ETH Zentrum, Sonneggstr. 5, Zuerich, 8092 Switzerland
AU: Gilli, A
EM: agilli@geology.ufl.edu
AF: University of Florida, Dept. of Geological Sciences, 241 Williamson Hall, PO Box 11210, Gainesville, FL 32611 United States
AU: Anselmetti, F S
EM: flavio@erdw.ethz.ch
AF: ETH, Geologisches Institut - ETH Zentrum, Sonneggstr. 5, Zuerich, 8092 Switzerland
AB: In analogy to their marine counterparts, iron oxyhydroxides in lacustrine sediments are potential archives of environmental change. Eolian particles, commonly coated with Fe oxides, are the most frequent source of detritic iron oxyhydroxides in lake basins. They provide a climate-sediment connection that is applied here to an ultra high-resolution study of a laminated core from Southern Patagonia. These results show fluctuations in the amount of iron oxyhydroxides covering the last ca. 1800 years that are attributed to past changes in wind intensity. Located at $49\deg$S on the Patagonian plateau of Argentina, Lago Cardiel closed-basin occupies a tectonic depression of ca. 20 km diameter and a maximum water depth of 76 m. Today, this very arid but sensitive rain-shadow area west of the Andes is seasonally influenced by the southern westerlies. Thus, the lake provides an ideal location to trace changes in their strength and influence on the local sedimentological regime through time. A ca. 10 m long sedimentary core with a high sedimentation rate of approximately 56 cm/100 yr allows the detailed study of laminated sediments with variable degree of development and thickness. Magnetic susceptibility microprofiles at one mm scale reveals comparatively higher values in the black laminae than the light olive grey silty clay. Analogously, these changes are mirrored by fluctuations in trace element content that may indicate a seasonal change in the influx of iron oxyhydroxides to the basin. Image analyses in the laminated sections of the core show a conspicuous frequency of changes that can be attributed to the forcing mechanisms behind their formation. Thus, these new data with a higher temporal resolution refine previous results from the same core and relate these changes to local wind activity, which seems to be directly induced by the intensification or weakening of the westerly storm tracks. Furthermore, it provides an independent proxy for wind intensity confirming previous studies that were based on indicators at a lower time resolution such as seismic stratigraphy and pollen analysis.
DE: 9360 South America
DE: 4863 Sedimentation
DE: 3344 Paleoclimatology
DE: 4239 Limnology
DE: 1845 Limnology
SC: Global Climate Change [GC]
MN: 2004 AGU Fall Meeting