Paleoecological and Stratigraphic Significance of the Muskrat in Pleistocene Deposits

Abstract

Research Article| December 01, 1970 Paleoecological and Stratigraphic Significance of the Muskrat in Pleistocene Deposits ROBERT S NELSON; ROBERT S NELSON Department of Geology, University of Iowa, Iowa City, Iowa 52240 AUTHOR'S PRESENT ADDRESS: DEPARTMENT OF GEOGRAPHY-GEOLOGY, ILLINOIS STATE UNIVERSITY, NORMAL, ILLINOIS 61761 (NELSON) Search for other works by this author on: GSW Google Scholar HOLMES A SEMKEN HOLMES A SEMKEN Department of Geology, University of Iowa, Iowa City, Iowa 52240 Search for other works by this author on: GSW Google Scholar Author and Article Information ROBERT S NELSON AUTHOR'S PRESENT ADDRESS: DEPARTMENT OF GEOGRAPHY-GEOLOGY, ILLINOIS STATE UNIVERSITY, NORMAL, ILLINOIS 61761 (NELSON) Department of Geology, University of Iowa, Iowa City, Iowa 52240 HOLMES A SEMKEN Department of Geology, University of Iowa, Iowa City, Iowa 52240 Publisher: Geological Society of America Received: 28 Apr 1970 Revision Received: 01 Jul 1970 First Online: 02 Mar 2017 Online Issn: 1943-2674 Print Issn: 0016-7606 Copyright © 1970, The Geological Society of America, Inc. Copyright is not claimed on any material prepared by U.S. government employees within the scope of their employment. GSA Bulletin (1970) 81 (12): 3733–3738. https://doi.org/10.1130/0016-7606(1970)81[3733:PASSOT]2.0.CO;2 Article history Received: 28 Apr 1970 Revision Received: 01 Jul 1970 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 ROBERT S NELSON, HOLMES A SEMKEN; Paleoecological and Stratigraphic Significance of the Muskrat in Pleistocene Deposits. GSA Bulletin 1970;; 81 (12): 3733–3738. doi: https://doi.org/10.1130/0016-7606(1970)81[3733:PASSOT]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 muskrat (Ondatra spp.), a common element in late Kansan and post-Kansan deposits, provides a valuable Stratigraphic tool for deposits of glacial age, in terms of the chronocline proposed by Semken (1966). However, specimens of interglacial age commonly appear out of sequence in the regression. In addition, the nearly ubiquitous distribution in North America of modern muskrats has precluded paleoecological interpretations other than for the presence of permanent water.Statistical analysis of 147 fossil first-lower molars of Ondatra substantiates and refines the established chronocline. Additionally, it reveals that specimens taken from deposits regarded as interglacial in age have a significantly lower length/width ratio than have those collected from deposits regarded as glacial in age. A statistical examination of 403 Recent first-lower molars from 26 of the United States and from Manitoba, Canada, indicates the following. (1) Both O. zibethicus zibethicus and O. z. cinnamonius found in southern regions exhibit a significantly lower length/width tooth ratio than do those found in northern regions. (2) The ratios, when plotted geographically, form a predictable north-south cline, which, although progressive, has a point of inflection at 42° N. lat. (Nebraska). Specimens collected to the north give a positive residual and southern specimens a negative residual to a least-squares regression. (3) O. z. zibethicus (eastern form) and O. z. cinnamonius (plains variety) are indistinguishable on dental parameters at any given latitude. In conclusion, the data suggest that the length/width ratio is a reliable tool in distinguishing between “warm” and “cool” associated members of the population. Corresponding differences in ratios in glacial and interglacial specimens support this hypothesis. The Hay Springs local fauna, as preserved in the American Museum of Natural History, probably represents a mixed collection, taken from more than one quarry, in a section where rocks of glacial and interglacial age are preserved. This content is PDF only. Please click on the PDF icon to access. First Page Preview Close Modal You do not have access to this content, please speak to your institutional administrator if you feel you should have access.