Laramide exhumation of the Bighorn Mountains, Wyoming: An apatite (U-Th)/He thermochronology study

Abstract

Research Article| January 01, 2002 Laramide exhumation of the Bighorn Mountains, Wyoming: An apatite (U-Th)/He thermochronology study Peter D. Crowley; Peter D. Crowley 1Department of Geology, Amherst College, Amherst, Massachusetts 01002, USA Search for other works by this author on: GSW Google Scholar Peter W. Reiners; Peter W. Reiners 2Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, California 91125, USA Search for other works by this author on: GSW Google Scholar Joanna M. Reuter; Joanna M. Reuter 3Department of Geology, Carleton College, Northfield, Minnesota 55057, USA Search for other works by this author on: GSW Google Scholar Grant D. Kaye Grant D. Kaye 4Department of Geology, Colorado College, Colorado Springs, Colorado 80903, USA Search for other works by this author on: GSW Google Scholar Author and Article Information Peter D. Crowley 1Department of Geology, Amherst College, Amherst, Massachusetts 01002, USA Peter W. Reiners 2Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, California 91125, USA Joanna M. Reuter 3Department of Geology, Carleton College, Northfield, Minnesota 55057, USA Grant D. Kaye 4Department of Geology, Colorado College, Colorado Springs, Colorado 80903, USA Publisher: Geological Society of America Received: 01 Mar 2001 Revision Received: 30 Jul 2001 Accepted: 03 Sep 2001 First Online: 02 Jun 2017 Online ISSN: 1943-2682 Print ISSN: 0091-7613 Geological Society of America Geology (2002) 30 (1): 27–30. https://doi.org/10.1130/0091-7613(2002)030<0027:LEOTBM>2.0.CO;2 Article history Received: 01 Mar 2001 Revision Received: 30 Jul 2001 Accepted: 03 Sep 2001 First Online: 02 Jun 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn Email Permissions Search Site Citation Peter D. Crowley, Peter W. Reiners, Joanna M. Reuter, Grant D. Kaye; Laramide exhumation of the Bighorn Mountains, Wyoming: An apatite (U-Th)/He thermochronology study. Geology 2002;; 30 (1): 27–30. doi: https://doi.org/10.1130/0091-7613(2002)030<0027:LEOTBM>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 We report (U-Th)/He apatite ages from the crystalline core of the Bighorn Mountains and compare the exhumation history derived from those ages with the exhumation history determined from sedimentary rocks in the adjacent Powder River and Bighorn basins. Our (U-Th)/He apatite ages range from 62 to 369 Ma and represent a pre-Laramide He partial retention zone that was deformed and uplifted at ca. 65 ± 5 Ma. The geometry of the He partial retention zone indicates that the basement in the Bighorn Mountains is deformed into a doubly plunging anticline. The preservation of a pre-Laramide partial retention zone in the upper few hundred meters of Precambrian basement indicates that in general, the temperature at the Cambrian unconformity did not exceed the apatite He closure temperature. This is difficult to reconcile with evidence from adjacent basins for thick sequences of sedimentary rocks (3–4 km) prior to 65 Ma, and normal modern geothermal gradients. Either the range was never deeply buried (<2–3 km), its geothermal gradient has been low (<20 °C) since at least the Mesozoic, or our apatites have higher (U-Th)/He closure temperatures (∼80–90 °C) than those measured for other apatites. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.