Document type: DU ETD
Collection: Geology Theses  
Title Sedimentological Evidence of Late Quaternary Environmental Change Preserved in a Grand Mesa, Colorado Peat Deposit
Author(s) Williams, Tennille J.
School/Department Department of Geography
Institution University of Denver
Degree Type Master's
Degree Name M.A.
Type of Resource text
Degree Date 2005 June
Digital Origin reformatted digital
Rights Statement All Rights Reserved
Reason for Restrictions No restrictions
Type of Restriction No restrictions
Keyword(s) Geography
Genre Dissertations, Academic
Abstract Kannah Creek Fen (elevation 3200 m) occupies a glaciated stream channel atop Grand Mesa, a basalt-capped plateau in western Colorado. Several cores (>7.5 m length) provide evidence of environmental change over the last 20,000 years. The upper 4.8 m of the cores are composed of peat; the lower 3 m are made up of silty lake mud and fine grained glacial outwash. A bulk sample radiocarbon date of 18,890 +/- 70 14C yr BP was obtained just above the bottom of the sediment core; peat began accumulating 10,040 +/- 4014 C yr·BP. Close interval sampling of sediment properties and fossil pollen were used to reconstruct a high resolution record of paleoenvironmental change. High bulk density values at the base of the core reflect the presence and eventual disappearance of the Grand Mesa ice cap near the end of the Pleistocene. Organic content of the peat can be used as a proxy of relative paleotemperature, and organic content curves from the fen cores approximate other paleotemperature proxy records from the region. Changes in the degree of humification of the peat, measured as percent light transmittance, provide a proxy for effective moisture. The humification data from periods during the Holocene that were warmer than today indicate that peat was more humified, suggesting that increased temperatures either did not strengthen the summer monsoon in the region, or that any increase in precipitation was offset by increased evapotransporation. The conclusions from this research provide a record of paleomoisture conditions and suggest a means of validating global climate models used to predict future climate.
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