2008 Joint Meeting of The Geological Society of America, Soil Science Society of America, American Society of Agronomy, Crop Science Society of America, Gulf Coast Association of Geological Societies with the Gulf Coast Section of SEPM

Paper No. 10
Presentation Time: 10:30 AM

Pleistocene-Holocene Fjord Sedimentation Associated with Temperate Tidewater Glaciers in Western Patagonia, South America

FERNÁNDEZ, Rodrigo A., Jackson School of Geosciences, U.T.I.G. - University of Texas Institute for Geophysics, J.J. Pickle Research Campus, Bldg. 196, 10100 Burnet Road (R2200), Austin, TX 78758-4445, ANDERSON, John B., Department of Earth Science, Rice University, 6100 Main Street, Houston, TX 77005 and WELLNER, Julia S., Department of Geosciences, University of Houston, 312 Science & Research Building 1, Houston, TX 77204-5007, r.f@ig.utexas.edu

Glacial erosion of mountains and sedimentation in adjacent fjords and on high-latitude continental shelves has become a major focus of research into landscape evolution, climate-tectonic linkages and paleoclimate evolution at different geographical and temporal scales. Special attention has been given to sediments deposited following the LGM as indicators of glacier erosion rates and sediment yields, particularly as they relate to climatic variables. We present the results of a study of three fjords that are the repositories of sediment delivered from temperate tidewater glaciers draining portions of the largest extant ice masses of the southern hemisphere outside Antarctica: the northern and southern Patagonian Ice fields and Cordillera Darwin Ice Cap. The study area covers a broad latitudinal range (46.7°-54.5° S) where zonal atmospheric circulation and the orographic effect of the Andes Cordillera create large latitudinal and longitudinal temperature and precipitation gradients. Temperature and precipitation diminish southward, while the size of drainage basins with respect to the fjords are comparable. The dataset includes swath bathymetry maps, seismic data, and results from core analyses. In general, the fjords are composed of a series of basins separated by shallow ridges and/or narrow passages that connect with a deep sound or channel. Rates of sedimentation diminish by roughly an order of magnitude with increasing distance from glacier termini, from meters per year for the most proximal and restricted basins to less than one millimeter per year for more distal basins. Sedimentation rates are the highest in the southernmost fjord, which is an unexpected result. Current research focuses on establishing sediment flux for each fjord throughout the Holocene.