TILL-PEBBLE ISOPLETH MAPS OF PARTS OF MONTANA AND NORTH DAKOTA

Abstract

Research Article| September 01, 1956 TILL-PEBBLE ISOPLETH MAPS OF PARTS OF MONTANA AND NORTH DAKOTA ARTHUR DAVID HOWARD ARTHUR DAVID HOWARD STANFORD UNIVERSITY, STANFORD, CALIF. Search for other works by this author on: GSW Google Scholar Author and Article Information ARTHUR DAVID HOWARD STANFORD UNIVERSITY, STANFORD, CALIF. Publisher: Geological Society of America Received: 03 Oct 1955 First Online: 02 Mar 2017 Online ISSN: 1943-2674 Print ISSN: 0016-7606 Copyright © 1956, 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 (1956) 67 (9): 1199–1206. https://doi.org/10.1130/0016-7606(1956)67[1199:TIMOPO]2.0.CO;2 Article history Received: 03 Oct 1955 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 ARTHUR DAVID HOWARD; TILL-PEBBLE ISOPLETH MAPS OF PARTS OF MONTANA AND NORTH DAKOTA. GSA Bulletin 1956;; 67 (9): 1199–1206. doi: https://doi.org/10.1130/0016-7606(1956)67[1199:TIMOPO]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 An isopleth map shows the distribution of a variable by lines of equal magnitude called isopleths. Till-pebble isopleth maps show the areal distribution of pebbles of different rock types in till.Four till-pebble isopleth maps were prepared during a reconnaissance study of the Pleistocene geology of northeastern Montana and northwestern North Dakota. Three of the maps are concerned with erratic pebbles; the fourth, with locally derived pebbles.The isopleth maps of the erratic pebbles reveal an area in northwestern North Dakota where the erratic content of the till differs significantly from that of the till elsewhere in the region. Lithologic relations are described which suggest that the drift of this small area may differ in age from that to the north and south.A till-pebble isopleth map of distinctive, locally derived fluvial pebbles reveals three large areas of till in which these pebbles are abundant. Two of the areas, southwest and west of extensive exposures of the source gravels, suggest that the ice moved generally southwestward across the area. The third area is unrelated to known gravel exposures and may indicate a body of gravel below the till.The study indicates that till-pebble isopleth maps may sometimes prove useful in suggesting the possibility of multiple drifts and in helping to delimit the drifts once substantiated. They may also provide information on direction of ice movement and on the identity of concealed bedrock. 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.