Transport Direction of Peoria Loess in Nebraska and Implications for Loess Sources on the Central Great Plains

• Published in: Quaternary Research
• Main Author: Mason, Joseph A.
• Format: Article in Journal/Newspaper
• Language: English
• Published: Cambridge University Press (CUP) 2001
• Subjects: Ice Sheet
• Online Access: http://dx.doi.org/10.1006/qres.2001.2250; http://api.elsevier.com/content/article/PII:S0033589401922501?httpAccept=text/xml; http://api.elsevier.com/content/article/PII:S0033589401922501?httpAccept=text/plain; https://www.cambridge.org/core/services/aop-cambridge-core/content/view/S0033589400010103

Abstract In the midwestern United States, large rivers draining the Laurentide Ice Sheet (LIS) were the most important sources of Peoria Loess, deposited during the last glaciation. Loess deposition near those rivers may have responded primarily to ice-sheet dynamics rather than direct effects of climatic change. In contrast, it has been proposed that thick Peoria Loess on the central Great Plains was derived mainly from unglaciated landscapes northwest of the main loess deposits. In this study, transport directions inferred from more than 600 measurements of Peoria Loess thickness in Nebraska are used to test the hypothesis that much of the Peoria Loess on the Great Plains is nonglaciogenic. A strong northwest to southeast thickness trend indicates that most Peoria Loess in Nebraska was transported from one or more unglaciated northwestern source areas rather than from glacially influenced river floodplains. The Missouri River (draining the LIS), the Platte River (draining alpine glaciers), and the Elkhorn River (unglaciated basin) were secondary sources. Their contribution is not detectable beyond a distance of 40–60 km. Peoria Loess deposition on the central Great Plains was largely a direct response to climatic change in the unglaciated source region.