Chronology and provenance of last-glacial (peoria) loess in western iowa and paleoclimatic implications

Geologic archives show that the Earth was dustier during the last glacial period. One model suggests that increased gustiness (stronger, more frequent winds) enhanced dustiness. We tested this at Loveland, Iowa, one of the thickest deposits of last-glacial-age (Peoria) loess in the world. Based on K...

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Bibliographic Details
Published inQuaternary research Vol. 80; no. 3; pp. 468 - 481
Main Authors Muhs, Daniel R., Bettis III, E. Arthur, Roberts, Helen M., Harlan, Stephen S., Paces, James B., Reynolds, Richard L.
Format Journal Article
LanguageEnglish
Published New York, USA Cambridge University Press 01.11.2013
Elsevier Inc
Subjects
Iowa
Last glacial period
Laurentide ice sheet
Magnetic minerals
Optically stimulated luminescence dating
Original Articles
Paleoclimate
Peoria loess
Stratigraphy
Trace element geochemistry
Iowa
Last glacial period
Optically stimulated luminescence dating
Paleoclimate
Peoria loess
Stratigraphy
Trace element geochemistry
Laurentide ice sheet
Magnetic minerals
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Summary:Geologic archives show that the Earth was dustier during the last glacial period. One model suggests that increased gustiness (stronger, more frequent winds) enhanced dustiness. We tested this at Loveland, Iowa, one of the thickest deposits of last-glacial-age (Peoria) loess in the world. Based on K/Rb and Ba/Rb, loess was derived not only from glaciogenic sources of the Missouri River, but also distal loess from non-glacial sources in Nebraska. Optically stimulated luminescence (OSL) ages provide the first detailed chronology of Peoria Loess at Loveland. Deposition began after ~ 27 ka and continued until ~ 17 ka. OSL ages also indicate that mass accumulation rates (MARs) of loess were not constant. MARs were highest and grain size was coarsest during the time of middle Peoria Loess accretion, ~ 23 ka, when ~ 10 m of loess accumulated in no more than ~ 2000 yr and possibly much less. The timing of coarsest grain size and highest MAR, indicating strongest winds, coincides with a summer-insolation minimum at high latitudes in North America and the maximum southward extent of the Laurentide ice sheet. These observations suggest that increased dustiness during the last glacial period was driven largely by enhanced gustiness, forced by a steepened meridional temperature gradient.
ISSN:0033-5894
1096-0287
DOI:10.1016/j.yqres.2013.06.006