Holocene Climate and Environmental Change from White Owl Lake Sediments, White River Plateau, Colorado

A Thesis submitted to the faculty of the Graduate School of the University of Minnesota by Marilyn Esther Kramer in partial fulfillment of the requirements for the degree of Master of Science, June 2009.This Masters project investigates the Holocene lacustrine sedimentary record of White Owl Lake (3,270 m), a small alpine lake located on the White River Plateau in west-central Colorado. Past changes in the watershed and within the lake are reflected in the sedimentary geochemical record; timing is constrained by radiocarbon ages. The combined data have been used to develop an age model and compare paleoclimatic and paleoenvironmental interpretations with findings from other nearby studies. Processes reflected in the geochemical record include development of terrestrial vegetation, lake basin evolution, changes in primary productivity, preservation of carbonates, changes in hydrology, and shifts in silicate provenance. Seismic-reflection profiles were used to select a site for sediment coring and to create a bathymetric map of White Owl Lake. Lithological changes in the White Owl Lake sedimentary record provide a unique opportunity to develop and calibrate a method to estimate the abundances of the major components of a typical lake sediment (carbonates, organic matter, and the residual mineral fraction) using scanning x-ray fluorescence (XRF) analysis and geochemical data from the core. The purpose of developing this method is to allow estimation of major components to guide decisions for other detailed analytical work. This research project is a part of a larger USGS project aimed at reconstructing changes in the Holocene hydrology and climate (hydroclimate) of the Upper Colorado River Basin, including the White River Plateau, using lake sediments. Interpretations from this project will add to the ongoing USGS study, and our understanding of millennial-scale Holocene climate variability on the plateau