Mason, Joseph A.
M.S. (Master of Science)
Department of Geography
Sand dunes--Illinois--Amboy; Paleoclimatology--Illinois--Amboy
Research on currently inactive dunes in Colorado and Nebraska reveals th a t they formed during widespread Holocene episodes of dune activity. This study focuses on the relative age of inactive dunes in northern Illinois on the late Wisconsinan Bloomington Moraine. If these dunes were active during the Holocene, they could be an important geomorphological proxy for Holocene climate change. Soils on one dune and in adjacent loesscovered areas were studied to determine the relative degree of soil development and to identify any buried soils under the dune. Ten soil profiles were described and analyzed for particle size, color, pH, and other physical properties. Wind speed and climatic data from a nearby station were used to calculate a mobility index and a sand rose to quantify the potential for eolian sand movement. The result was th a t there was enough wind energy for sand movement; however the P/PE is high enough for stable vegetation cover and therefore stable dunes. The orientation of the dunes indicates northwest winds during their formation. Soils in the dune sand and in the loess both have clay accumulations in Bt horizons, although those in the dune sand are much more weakly developed. This may reflect differences in parent material rath e r th an age. The presence of a Bt horizon indicates the soils are more than a few hundred years old, probably significantly older. There are no buried soil horizons under the dune, which rests on unweathered late Wisconsinan glacial till. This means the sands were deposited not long after the till or if there were soils on the till before the sands, they were completley eroded away before the sands migrated in. It is concluded th a t the dune most probably formed more than 10,000 years B.P., under cold climate conditions, rather than during warm, dry parts of the Holocene.
Troast, Jennifer L., "The relative age and paleoclimatic implications of a sand dune in Amboy, Illinois" (1998). Graduate Research Theses & Dissertations. 6212.
Northern Illinois University
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