INTERPRETING SOILS AND WEATHERING CHARACTERISTICS TO DIFFERENTIATE GLACIAL DEPOSITS IN THE BIGHORN MOUNTAINS, WYOMING: THE INFLUENCE OF DR. ROBERT D. HALL

Although Bob Hall is known for his work on the mid-continent paleosols in glacial till and loess, he is also well known for his work describing and mapping alpine glacial deposits in places like the Wind River Range in Wyoming and the Tobacco Root mountains in southwest Montana. Bob's interest in pedology and alpine glaciations is contagious, and fueled my own interest in glacial deposits and soils. To this day, I still appreciate soils, and cannot remember more enjoyable times than working with Bob mapping and sampling moraines in the Tobacco Roots.

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.