Long-distance longitudinal transport of gravel across the Cordilleran thrust belt of Montana and Idaho

Abstract

Research Article| May 01, 2000 Long-distance longitudinal transport of gravel across the Cordilleran thrust belt of Montana and Idaho Susanne U. Janecke; Susanne U. Janecke 1Department of Geology, Utah State University, Logan, Utah 84322-4505, USA Search for other works by this author on: GSW Google Scholar Colby J. VanDenburg; Colby J. VanDenburg 1Department of Geology, Utah State University, Logan, Utah 84322-4505, USA Search for other works by this author on: GSW Google Scholar James J. Blankenau; James J. Blankenau 1Department of Geology, Utah State University, Logan, Utah 84322-4505, USA Search for other works by this author on: GSW Google Scholar John W. M'Gonigle John W. M'Gonigle 2U.S. Geological Survey, Federal Center, Denver, Colorado 80225, USA Search for other works by this author on: GSW Google Scholar Geology (2000) 28 (5): 439–442. https://doi.org/10.1130/0091-7613(2000)28<439:LLTOGA>2.0.CO;2 Article history received: 18 Oct 1999 rev-recd: 09 Feb 2000 accepted: 16 Feb 2000 first online: 02 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 Susanne U. Janecke, Colby J. VanDenburg, James J. Blankenau, John W. M'Gonigle; Long-distance longitudinal transport of gravel across the Cordilleran thrust belt of Montana and Idaho. Geology 2000;; 28 (5): 439–442. doi: https://doi.org/10.1130/0091-7613(2000)28<439:LLTOGA>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 SocietyGeology Search Advanced Search Abstract Two newly identified middle Eocene paleovalleys (≥ 100 km long) preserved on top of the southwest Montana reentrant of the Cordilleran fold-and-thrust belt indicate long-lived longitudinal flow across the thrust belt and resolve a long-standing debate about the source of the voluminous quartzite debris in the Upper Cretaceous to lower Tertiary Divide, Harebell, and Pinyon conglomerates of Montana, Idaho, and Wyoming. Geologic mapping, stratigraphic, provenance, and geochronologic studies revealed that Eocene volcanic and sedimentary rocks in the paleovalleys are as thick as 2 km, onlap preexisting bedrock, and interfinger with well-rounded conglomerate derived from formations exposed only to the west. The middle Eocene paleovalleys are the youngest expression of a major paleoriver system that transported sediment toward the foreland during the Sevier orogeny. An Eocene subcrop map shows that the headwaters of the Eocene paleovalleys coincided with structural culminations in the thrust belt that supplied sediment to the Divide conglomerate of the Upper Cretaceous to lower Tertiary Beaverhead Group. Ultimately, the Lemhi Pass and Hawley Creek paleovalleys provided several thousand cubic kilometers of quartzite debris to the Pinyon and Harebell conglomerates of northwest Wyoming 200–350 km away, and formed the northwest half of a giant longitudinal drainage system. Sevier contraction, not the rising Idaho batholith, first uplifted vast culminations beneath the headwaters of this river system. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.