Glacial stratigraphy and paleomagnetism of late Cenozoic deposits of the north-central United States

Research Article| January 01, 2004 Glacial stratigraphy and paleomagnetism of late Cenozoic deposits of the north-central United States M. Roy; M. Roy 1Department of Geosciences, Oregon State University, Corvallis, Oregon 97331-5506, USA Search for other works by this author on: GSW Google Scholar P.U. Clark; P.U. Clark 1Department of Geosciences, Oregon State University, Corvallis, Oregon 97331-5506, USA Search for other works by this author on: GSW Google Scholar R.W. Barendregt; R.W. Barendregt 2Faculty of Art and Science, University of Lethbridge, Lethbridge, Alberta T1K 3M4, Canada Search for other works by this author on: GSW Google Scholar J.R. Glasmann; J.R. Glasmann 3Department of Geosciences, Oregon State University, Corvallis, Oregon 97331-5506, USA Search for other works by this author on: GSW Google Scholar R.J. Enkin R.J. Enkin 4Geological Survey of Canada-Pacific, Sidney, British Columbia V8L 4B2, Canada Search for other works by this author on: GSW Google Scholar GSA Bulletin (2004) 116 (1-2): 30–41. https://doi.org/10.1130/B25325.1 Article history received: 31 Jan 2003 rev-recd: 27 Jun 2003 accepted: 12 Jul 2003 first online: 02 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation M. Roy, P.U. Clark, R.W. Barendregt, J.R. Glasmann, R.J. Enkin; Glacial stratigraphy and paleomagnetism of late Cenozoic deposits of the north-central United States. GSA Bulletin 2004;; 116 (1-2): 30–41. doi: https://doi.org/10.1130/B25325.1 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 north-central United States preserves one of the best continental records of late Pliocene and early-middle Pleistocene glaciations in the Northern Hemisphere. The glaciogenic sequences of this region consist of multiple tills interbedded with paleosols and volcanic ashes. Here we present results on paleomagnetic measurements and till compositional data from glacial sedimentary sequences in Iowa, Nebraska, Kansas, and Missouri. Periods of normal polarity (Brunhes Chron) and reverse polarity (Matuyama Chron) were identified in the sedimentary sequences investigated. This chronology is further constrained by the presence of three volcanic ashes derived from dated eruptions of the Yellowstone caldera, which indicate that the oldest till was deposited >2.0 Ma. Based on these results we identify three groups of tills representing at least seven pre–Illinoian glaciations: two older groups of reverse-polarity tills containing low and intermediate proportions of crystalline clasts, respectively, and one younger group of normal-polarity tills enriched in crystalline lithologies. The clay mineralogy of the reverse-polarity tills is enriched in kaolinite and depleted in expandable clays relative to the normal-polarity tills, which are also characterized by a minor amount of chlorite. The silt fraction of tills also shows mineralogical contrasts whereby the normal-polarity tills are characterized by increases in calcite, dolomite, and feldspar, whereas the older tills show depletion in these minerals and a relative enrichment in quartz. These petrographic and mineralogic changes are indicative of an increase with time in the areal distribution of unweathered igneous and metamorphic source bedrock. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.