1 Living in Ruhe’s Shadow with Loess, Paleosols, and Tills: A Session in Honor of Bob Hall’s Contributions to Quaternary Science
Thursday, 24 April 2008
8:20 AM - 12:00 PM
INTERPRETING SOILS AND WEATHERING CHARACTERISTICS TO DIFFERENTIATE GLACIAL DEPOSITS IN THE BIGHORN MOUNTAINS, WYOMING: THE INFLUENCE OF DR. ROBERT D. HALL
Paper number: 1-10
Program: SYMPOSIA SESSIONS
Time: 11:20 AM – 11:40 AM
Authors
Abstract
In the Bighorn Mountains of Wyoming, surficial deposits were mapped in Paint Rock Creek valley above the confluence with Middle Paint Rock Creek up to Lake Solitude. Deposits were differentiated using stratigraphic relationships, valley position, moraine morphology, soil development, and clast weathering data. The study area contains deposits of two glaciations, with multiple stades in the younger glaciation, and likely in the older. Statistical analyses (discriminant analysis and hypothesis testing) of clast-weathering data provide reliable separation of Illinoian (Bull lake) and Wisconsinan (Pinedale) Age deposits, but could not separate intrastadial advances. Pinedale glacial deposits were separated into stades II and I based primarily on spatial relationships and soils data analysis. Soils and geomorphic evidence also suggests multiple Bull Lake stades, and possible pre-Bull Lake and Holocene advances. Soil data also indicate strong eolian silt input at higher elevations and colluvial influence at lower positions on the landscape.
Variations in clast lithology, clast texture, vegetation, topographic relief, and methodology explain differences in clast weathering between this study and previous Bighorn Mountain glacial studies. A comparison of soils from tills in Paint Rock Creek and other valleys showed consistency between geographic locations, indicating that climatic conditions and other soil forming factors were similar throughout the Bighorns.