Glacial and nonglacial sediment contributions to Wisconsin Episode loess in the central United States

Abstract

Research Article| October 01, 2000 Glacial and nonglacial sediment contributions to Wisconsin Episode loess in the central United States David A. Grimley David A. Grimley 1Illinois State Geological Survey, 615 East Peabody Drive, Champaign, Illinois 61820, USA Search for other works by this author on: GSW Google Scholar Author and Article Information David A. Grimley 1Illinois State Geological Survey, 615 East Peabody Drive, Champaign, Illinois 61820, USA Publisher: Geological Society of America Received: 08 Feb 1999 Revision Received: 07 Sep 1999 Accepted: 22 Nov 1999 First Online: 01 Jun 2017 Online ISSN: 1943-2674 Print ISSN: 0016-7606 Geological Society of America GSA Bulletin (2000) 112 (10): 1475–1495. https://doi.org/10.1130/0016-7606(2000)112<1475:GANSCT>2.0.CO;2 Article history Received: 08 Feb 1999 Revision Received: 07 Sep 1999 Accepted: 22 Nov 1999 First Online: 01 Jun 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation David A. Grimley; Glacial and nonglacial sediment contributions to Wisconsin Episode loess in the central United States. GSA Bulletin 2000;; 112 (10): 1475–1495. doi: https://doi.org/10.1130/0016-7606(2000)112<1475:GANSCT>2.0.CO;2 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGSA Bulletin Search Advanced Search Abstract The relative contributions of various glacial and nonglacial sediments to Wisconsin Episode loess units along the lower Illinois and central Mississippi Valleys are estimated on the basis of a comparison of magnetic susceptibility and silt and clay mineralogy. A mathematical method of source area calculation, using four compositional parameters, was guided by current knowledge of the regional glacial history. On the basis of this technique, the Roxana Silt, along the Illinois and Mississippi River Valleys, is composed of significant Superior lobe sediment (35%–40%) as well as Wadena or Des Moines lobe sediment (about 35%). This can account for its high magnetic susceptibility, feldspar content, kaolinite content, and pink hue. Lower Peoria Silt contains about 25%–35% Lake Michigan lobe sediment with reduced contributions of the other sources. After the Mississippi River's diversion (20.4 ka), the supply of Superior, Des Moines, and Wadena lobe sediment was cut off from the Illinois Valley in favor of Lake Michigan lobe sediment (75%–80% contribution). This major source area shift accounts for higher dolomite and illite contents and a more yellow hue in approximately the upper two-thirds of Peoria Silt in the study area. In loess south of St. Louis, less pronounced compositional shifts occur because Superior lobe sediment was not cut off and because Des Moines lobe, Wadena lobe, and Missouri River sediments, having more intermediate composition, compose 40%–50% of the loess, thereby diluting other source area changes. Nonglacial sediment, from fluvial and periglacial sources, is estimated to compose 10%–40% of loess in both regions. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.