Age, genesis, and paleoclimatic interpretation of the Sangamon/Loveland complex in the Lower Mississippi Valley, U.S.A.

Abstract

Research Article| January 01, 2011 Age, genesis, and paleoclimatic interpretation of the Sangamon/Loveland complex in the Lower Mississippi Valley, U.S.A. Helaine W. Markewich; Helaine W. Markewich † 1U.S. Geological Survey, 3039 Amwiler Road, Suite 130, Atlanta, Georgia 30360, USA †E-mail: [e-mail] Search for other works by this author on: GSW Google Scholar Douglas A. Wysocki; Douglas A. Wysocki 2National Soil Survey Center, 100 Centennial Mall North, Room 152, MS 34, Lincoln, Nebraska 68508, USA Search for other works by this author on: GSW Google Scholar Milan J. Pavich; Milan J. Pavich 3U.S. Geological Survey, National Center, MS 926B, Reston, Virginia 20192, USA Search for other works by this author on: GSW Google Scholar E. Moye Rutledge E. Moye Rutledge 4Emeritus Faculty, Department of Crop, Soil, and Environmental Sciences, University of Arkansas, Fayetteville, Arkansas 72701, USA Search for other works by this author on: GSW Google Scholar GSA Bulletin (2011) 123 (1-2): 21–39. https://doi.org/10.1130/B30208.1 Article history received: 02 Nov 2009 rev-recd: 11 Feb 2010 accepted: 06 Apr 2010 first online: 08 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 Helaine W. Markewich, Douglas A. Wysocki, Milan J. Pavich, E. Moye Rutledge; Age, genesis, and paleoclimatic interpretation of the Sangamon/Loveland complex in the Lower Mississippi Valley, U.S.A.. GSA Bulletin 2011;; 123 (1-2): 21–39. doi: https://doi.org/10.1130/B30208.1 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 For more than a century, the Sangamon paleosol (the Sangamon) has been an integral part of geologic and pedologic investigations in the central United States, including the Upper Mississippi and Lower Missouri River Valleys. Compositional, pedologic, micromorphologic, stratigraphic, and age data indicate that the prominent reddish paleosol developed in silt-rich deposits of the Lower Mississippi Valley, from southernmost Illinois to northwestern Mississippi, represents multiple periods of soil formation, and is wholly or in part time equivalent to the Sangamon of the central United States. Thermoluminescence data, for localities where the Sangamon developed in loess, indicate that the primary period of loess deposition was from 190 to 130 ka (oxygen isotope stage, OIS6), that loess deposition continued intermittently from 130 to 74 ka (OIS5), and that deposition was wholly or in part coeval with Loveland loess deposition in the central United States. Beryllium-10, chemical, and pedologic data indicate that in the Lower Mississippi Valley: (1) the Sangamon represents a minimum time period of 60–80 k.y.; (2) there were at least two periods of soil formation, ca. 130–90 ka and 74–58 ka (OIS4); and (3) rates of weathering and pedogenesis equaled or exceeded the net loess-accumulation rate until at least 46 ka (OIS3) and resulted in development of a paleosol in the overlying basal Roxana Silt. Along a N-S transect from southern Illinois to western Mississippi, Sangamon macroscopic characteristics as well as the micromorphology, chemistry, and mineralogy, suggest a regional paleoclimate during periods of soil formation that: (1) was warm to hot, with a wider range in temperature, precipitation, and evapotranspiration than present; (2) had seasonal to decadal or longer periods of drought; and (3) had down-valley (southward) trends of increasing temperature and precipitation and decreasing seasonality and variation in annual to decadal precipitation. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.