Last-glacial dustiness and enhanced gustiness: deciphering the record of Peoria Loess deposition at Loveland, western Iowa
Abstract
The Loveland Paratype Section (N41.50052°, W95.88934°) in western Iowa, USA, preserves one of the thickest deposits of last-glacial (Peoria) loess in the world. As such, this site offers an ideal opportunity to test the recently proposed idea that the enhanced global ';dustiness' which is widely noted across a range of Quaternary records during the Last Glacial Maximum (LGM), was primarily driven by increased ';gustiness' in the form of stronger, more frequent winds (McGee et al., 2010). Twenty-two quartz optically stimulated luminescence (OSL) ages taken from the Pisgah and Peoria Loess units at Loveland give ages that are stratigraphically consistent within uncertainties. Mass Accumulation Rates (MARs) calculated for the loess using both a linear accumulation rate model and also a Bayesian model of accumulation, show that the MAR varies significantly between the Pisgah and Peoria Loess. The MARs calculated for the Peoria Loess are among the highest last-glacial MARs in the world, but they are also shown to vary significantly over time within the Peoria Loess unit. The maximum Peoria Loess MARs are observed at ~23 ka, and they coincide with an increase in grain size identified for the middle Peoria unit by Muhs and Bettis (2000), implying a strengthening of winds at Loveland. At this time, the Laurentide Ice Sheet was at its maximum southward extent and insolation was at a minimum at high latitudes in North America, giving rise to an enhanced latitudinal temperature contrast. Such conditions, and the MAR and grain-size observations at Loveland, support the hypothesis that enhanced gustiness, generated by a steepened meridional temperature gradient, may have been a primary driver of last-glacial dustiness. References McGee, D., Broecker, W.S., and Winckler, G., 2010. Gustiness: the driver of glacial dustiness? Quaternary Science Reviews 29, 2340-2350. Muhs, D.R., and Bettis III, E.A., 2000. Geochemical variations in Peoria Loess of western Iowa indicate paleowinds of midcontinental North America during last glaciation. Quaternary Research 53, 49-61.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2013
- Bibcode:
- 2013AGUFMPP11B1808R
- Keywords:
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- 1100 GEOCHRONOLOGY;
- 1600 GLOBAL CHANGE;
- 9350 GEOGRAPHIC LOCATION North America;
- 1620 GLOBAL CHANGE Climate dynamics