HR: 0800h
AN: PP31A-1502    [Abstracts]
TI: Tracking tectonic activity and climate change in Southernmost Patagonia - The Lago Fagnano record
AU: * Waldmann, N
EM: nicolas.waldmann@terre.unige.ch
AF: University of Geneva, 13 Rue des Maraichers, Geneva, 1205 Switzerland
AU: Ariztegui, D
EM: daniel.ariztegui@terre.unige.ch
AF: University of Geneva, 13 Rue des Maraichers, Geneva, 1205 Switzerland
AU: Anselmetti, F S
EM: flavio@erdw.ethz.ch
AF: ETH, Sonneggstrasse 5, Zurich, 8092 Switzerland
AU: Austin, J A
EM: jamie@utig.ig.utexas.edu
AF: University of Texas at Austin, 4412 Spicewood Rd., TX, 78759 United States
AU: Moy, C
EM: moyc@stanford.edu
AF: Standford University, 325 Braun Hall, CA, 94305 United States
AU: Dunbar, R
EM: dunbar@stanford.edu
AF: Standford University, 325 Braun Hall, CA, 94305 United States
AB: The climate of southernmost Patagonia is influenced by the westerly winds, the Southern Ocean circumpolar flow, and the South Pacific gyre. Therefore, continental sediment records from this area are ideal to track high-latitude climate variability through time. Located at 55° S in Tierra del Fuego, Lago Fagnano occupies the deepest of a chain of tectonic depressions along the Fagnano-Magallanes fault system. Fagnano is the biggest (~110 km long), southernmost non-ice covered lake in the world. In March 2005, >800 km of geophysical data were acquired in the lake, combining simultaneously 3.5 kHz (pinger) single-channel with 1 in³ airgun multi-channel systems. These data provide a unique opportunity to look at the most recent lacustrine sediments with high-resolution, while imaging the oldest sediments at the same time. Preliminary interpretations show that the lake is divided into two sub-basins: a deep eastern sub-basin (~200 m water depth), and a shallower western sub-basin (~100 m). The seismic survey penetrated more than several tens of meters of sediments, exhibiting both lacustrine and glacial provenance, probably comprising the LGM and the Holocene. Seismic reflectors indicate the presence of neo-tectonic structures affecting even the most recent sedimentary package, including some mega-turbidites, suggesting continuing tectonic impact on sedimentation. Gravity cores from both sub-basins reveal a regular alternation of light and dark laminae with abundant diatom content. Ultra-high resolution X-ray fluorescence micro-profiles show fluctuations at mm scale in major and trace elements that may indicate seasonal influx changes into the basin. These core data will provide a unique record of decadal changes in regional climate that will be compared with other marine and continental archives to improve our understanding of the forcing mechanisms behind climate change that can be further used to validate the outcome of ocean and atmospheric climatic models for the Southern Hemisphere. We are also using the interpreted seismic profiles to identify piston coring sites, for field operations anticipated in 2006.
DE: 0473 Paleoclimatology and paleoceanography (3344, 4900)
DE: 0746 Lakes (9345)
DE: 0935 Seismic methods (3025, 7294)
DE: 1616 Climate variability (1635, 3305, 3309, 4215, 4513)
DE: 4942 Limnology (0458, 1845, 4239)
SC: Paleoceanography and Paleoclimatology [PP]
MN: Fall Meeting 2005