Indiana University Purdue University Indianapolis

ES Colloquium Series: Monday January 27, Dr. Henry Loope, IN Geological Survey

Monday, 27 January 2014 - 12:00pm - 1:00pm
Dr. Henry Loope "Chronology and paleoenvironmental significance of eolian sand activity south of the Laurentide Ice Sheet during the last glacial period, Upper Mississippi River basin"
SL 165

Please join us from 12:00 - 1:00 pm in SL165 to hear from Dr. Henry Loope of the Quaternary Mapping group of the Indiana Geological Survey. Dr. Loope will present on "Chronology and paleoenvironmental significance of eolian sand activity south of the Laurentide Ice Sheet during the last glacial period, Upper Mississippi River basin"

ABSTRACT: Wind-blown sediments of the North American midcontinent provide important information regarding past climate and terrestrial processes during the Quaternary. An accurate chronology of eolian activity is needed to compare with other records of paleoenvironmental change, including advance/retreat of the Laurentide Ice Sheet and paleoecological records of vegetation change. This project employs optically stimulated luminescence (OSL, aka optical) dating to determine the depositional age of eolian sand within the Upper Mississippi River basin in order to reconstruct the timing of past changes in surface sand availability and atmospheric circulation. Twenty nine optical ages on eolian sand range in age from ca. 20 to 13 ka with the majority of ages clustered around 16 ka. The bulk of ages fall near the end of an interval documented by previous research within the study area indicating periglacial mass wasting between ca. 23 and 14 k cal yr BP based on radiocarbon ages on wood and gastropods from colluvium. Significant retreat of the Lake Michigan and Des Moines Lobes of the Laurentide Ice Sheet also occurred after 16 ka, and the final record of tundra-like vegetation and permafrost in the study area occurs near 16 ka. Optical ages on eolian sand from several distinct geomorphic settings, including fluvial (fill terrace) sediments from both glaciated and unglaciated fluvial catchments and colluvium derived from Cambrian sandstones overlap within error at ca. 16 ka, suggesting a regional eolian response rather than localized responses due to changes in sediment supply. I hypothesize that the regional eolian response is ultimately forced by changes in atmospheric circulation and surface conditions associated with the melting of permafrost.