230Th/U dating of a late Pleistocene alluvial fan along the southern San Andreas fault

Abstract

Research Article| September 01, 2010 230Th/U dating of a late Pleistocene alluvial fan along the southern San Andreas fault Kathryn E.K. Fletcher; Kathryn E.K. Fletcher 1Department of Earth and Planetary Science, University of California–Berkeley, Berkeley, California 94720-4767, USA Search for other works by this author on: GSW Google Scholar Warren D. Sharp; Warren D. Sharp 2Berkeley Geochronology Center, 2455 Ridge Road, Berkeley, California 94709, USA Search for other works by this author on: GSW Google Scholar Katherine J. Kendrick; Katherine J. Kendrick 3U.S. Geological Survey, 525 South Wilson Ave., Pasadena, California 91106, USA Search for other works by this author on: GSW Google Scholar Whitney M. Behr; Whitney M. Behr 4Department of Earth Sciences, University of Southern California, 3651 Trousdale Parkway, Los Angeles, California 90089, USA Search for other works by this author on: GSW Google Scholar Kenneth W. Hudnut; Kenneth W. Hudnut 3U.S. Geological Survey, 525 South Wilson Ave., Pasadena, California 91106, USA Search for other works by this author on: GSW Google Scholar Thomas C. Hanks Thomas C. Hanks 5U.S. Geological Survey, 345 Middlefield Road, Menlo Park, California 94025, USA Search for other works by this author on: GSW Google Scholar Author and Article Information Kathryn E.K. Fletcher 1Department of Earth and Planetary Science, University of California–Berkeley, Berkeley, California 94720-4767, USA Warren D. Sharp 2Berkeley Geochronology Center, 2455 Ridge Road, Berkeley, California 94709, USA Katherine J. Kendrick 3U.S. Geological Survey, 525 South Wilson Ave., Pasadena, California 91106, USA Whitney M. Behr 4Department of Earth Sciences, University of Southern California, 3651 Trousdale Parkway, Los Angeles, California 90089, USA Kenneth W. Hudnut 3U.S. Geological Survey, 525 South Wilson Ave., Pasadena, California 91106, USA Thomas C. Hanks 5U.S. Geological Survey, 345 Middlefield Road, Menlo Park, California 94025, USA †E-mail: fletcher@eps.berkeley.edu Publisher: Geological Society of America Received: 31 Jan 2009 Revision Received: 18 Jun 2009 Accepted: 03 Jul 2009 First Online: 08 Mar 2017 Online ISSN: 1943-2674 Print ISSN: 0016-7606 © 2010 Geological Society of America GSA Bulletin (2010) 122 (9-10): 1347–1359. https://doi.org/10.1130/B30018.1 Article history Received: 31 Jan 2009 Revision Received: 18 Jun 2009 Accepted: 03 Jul 2009 First Online: 08 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 Kathryn E.K. Fletcher, Warren D. Sharp, Katherine J. Kendrick, Whitney M. Behr, Kenneth W. Hudnut, Thomas C. Hanks; 230Th/U dating of a late Pleistocene alluvial fan along the southern San Andreas fault. GSA Bulletin 2010;; 122 (9-10): 1347–1359. doi: https://doi.org/10.1130/B30018.1 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 U-series dating of pedogenic carbonate-clast coatings provides a reliable, precise minimum age of 45.1 ± 0.6 ka (2σ) for the T2 geomorphic surface of the Biskra Palms alluvial fan, Coachella Valley, California. Concordant ages for multiple subsamples from individual carbonate coatings provide evidence that the 238U-234U-230Th system has remained closed since carbonate formation. The U-series minimum age is used to assess previously published 10Be exposure ages of cobbles and boulders. All but one cobble age and some boulder 10Be ages are younger than the U-series minimum age, indicating that surface cobbles and some boulders were partially shielded after deposition of the fan and have been subsequently exhumed by erosion of fine-grained matrix to expose them on the present fan surface. A comparison of U-series and 10Be ages indicates that the interval between final alluvial deposition on the T2 fan surface and accumulation of dateable carbonate is not well resolved at Biskra Palms; however, the “time lag” inherent to dating via U-series on pedogenic carbonate can be no larger than ∼10 k.y., the uncertainty of the 10Be-derived age of the T2 fan surface. Dating of the T2 fan surface via U-series on pedogenic carbonate (minimum age, 45.1 ± 0.6 ka) and 10Be on boulder-top samples using forward modeling (preferred age, 50 ± 5 ka) provides broadly consistent constraints on the age of the fan surface and helps to elucidate its postdepositional development. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.