Understanding Ice Age Climate in Buffalo Gap National Grasslands through Heavy Mineral Analysis

Understanding Ice Age Climate in Buffalo Gap National Grasslands through Heavy Mineral Analysis

Alvin Sherman Library

More information about ice age climate change during Marine Isotope Stage 2 (MIS 2), the last glacial maximum, is known from ice cores and marine sediments than from continental geology. For scientists to construct climate models, they need climate information about continental areas for comparison. Marine and ice sediments are deposited in layers, year after year, with relatively little disturbance after deposition. Changes in isotopic composition of these sediments reflect profound changes in Earth's climate. The equivalent continental sediment record is loess (windblown dust), which is deposited in fine layers without subsequent disturbance. Here, we studied loess to determine paleowind direction in this section of the North American Great Plains. The field area, located in the Buffalo Gap National Grasslands, is a midcontinental area that was within 250 km of the ice margin at the coldest period of MIS2. Wind direction may have been influenced by the proximity to the ice margin when the glacier was at its maximum extent. This would have influenced wind speed, wind direction, and hydroclimate of the region. In this study, we used heavy mineral analysis to determine paleowind direction during the last glacial maximum. Accessory minerals, which are uncommon minerals often characteristic of their source, were separated from loess and possible source(s) using heavy liquids. We used transmission and reflected light microscopy to identify and quantify accessory minerals from possible sources including major rivers (Cheyenne and White Rivers), tributary streams, and bedrock. Identification of the loess source based on mineral compositions will be presented.