Pleistocene relief production in Laramide mountain ranges, western United States

Research Article| February 01, 1998 Pleistocene relief production in Laramide mountain ranges, western United States Eric E. Small; Eric E. Small 1Department of Earth Sciences and Institute for Tectonics, University of California, Santa Cruz, California 95064 Search for other works by this author on: GSW Google Scholar Robert S. Anderson Robert S. Anderson 1Department of Earth Sciences and Institute for Tectonics, University of California, Santa Cruz, California 95064 Search for other works by this author on: GSW Google Scholar Author and Article Information Eric E. Small 1Department of Earth Sciences and Institute for Tectonics, University of California, Santa Cruz, California 95064 Robert S. Anderson 1Department of Earth Sciences and Institute for Tectonics, University of California, Santa Cruz, California 95064 Publisher: Geological Society of America First Online: 02 Jun 2017 Online ISSN: 1943-2682 Print ISSN: 0091-7613 Geological Society of America Geology (1998) 26 (2): 123–126. https://doi.org/10.1130/0091-7613(1998)0262.3.CO;2 Article history First Online: 02 Jun 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn Email Permissions Search Site Citation Eric E. Small, Robert S. Anderson; Pleistocene relief production in Laramide mountain ranges, western United States. Geology 1998;; 26 (2): 123–126. doi: https://doi.org/10.1130/0091-7613(1998)0262.3.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 Gently sloped summits and ridges (collectively referred to as summit flats) are abundant in many Laramide ranges in the western United States. The erosion rate of summit flats is ∼10 m/m.y., on the basis of the concentrations of cosmogenic radionuclides. Because erosion rates in valleys between summit flats are an order of magnitude faster, relief within these ranges is currently increasing by about 100 m/m.y. If summit-flat erosion is slower than rock uplift driven by the isostatic response to valley erosion, then this relief production could result in increased summit elevations. The mean depth of material eroded from a smooth surface fit to existing summit flats varies from 280 to 340 m in four Laramide ranges, based on geographic information system (GIS) analyses of digital elevation models. This erosion would result in a maximum of 250–300 m of rock uplift, assuming Airy isostasy. However, because the Laramide ranges examined here are narrow relative to the flexural wavelength of the lithosphere, erosionally driven rock uplift is limited to ∼50–100 m. Over the past several million years, summit erosion would approximately offset this rock uplift. Therefore, we conclude that summit elevations have remained essentially constant even though several hundred meters of relief has been produced. On the basis of valley and summit erosion rates and the average depth of erosion, we estimate that relief production in Laramide ranges began at ca. 3 Ma. We hypothesize that this relief production was climatically driven and was associated with the onset or enhancement of alpine glaciation in these ranges. 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.