Estimation of slip rates in the southern Tien Shan using cosmic ray exposure dates of abandoned alluvial fans

Abstract

Research Article| March 01, 1998 Estimation of slip rates in the southern Tien Shan using cosmic ray exposure dates of abandoned alluvial fans Erik Thorson Brown; Erik Thorson Brown 1Centre de Spectrométrie Nucléaire et de Spectrométrie de Masse, CNRS-IN2P3, Bâtiment 108, F-91405 Campus Orsay, France Search for other works by this author on: GSW Google Scholar Didier L. Bourlés; Didier L. Bourlés 1Centre de Spectrométrie Nucléaire et de Spectrométrie de Masse, CNRS-IN2P3, Bâtiment 108, F-91405 Campus Orsay, France Search for other works by this author on: GSW Google Scholar Grant M. Raisbeck; Grant M. Raisbeck 1Centre de Spectrométrie Nucléaire et de Spectrométrie de Masse, CNRS-IN2P3, Bâtiment 108, F-91405 Campus Orsay, France Search for other works by this author on: GSW Google Scholar Françoise Yiou; Françoise Yiou 1Centre de Spectrométrie Nucléaire et de Spectrométrie de Masse, CNRS-IN2P3, Bâtiment 108, F-91405 Campus Orsay, France Search for other works by this author on: GSW Google Scholar B. Clark Burchfiel; B. Clark Burchfiel 2Department of Earth, Atmospheric and Planetary Sciences, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 Search for other works by this author on: GSW Google Scholar Peter Molnar; Peter Molnar 2Department of Earth, Atmospheric and Planetary Sciences, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 Search for other works by this author on: GSW Google Scholar Deng Qidong; Deng Qidong 3Institute of Geology, State Seismology Bureau, Beijing, China Search for other works by this author on: GSW Google Scholar Li Jun Li Jun 4Provincial Bureau of Seismology, State Seismology Bureau, Urumqi, Xinjiang, China Search for other works by this author on: GSW Google Scholar Author and Article Information Erik Thorson Brown 1Centre de Spectrométrie Nucléaire et de Spectrométrie de Masse, CNRS-IN2P3, Bâtiment 108, F-91405 Campus Orsay, France Didier L. Bourlés 1Centre de Spectrométrie Nucléaire et de Spectrométrie de Masse, CNRS-IN2P3, Bâtiment 108, F-91405 Campus Orsay, France Grant M. Raisbeck 1Centre de Spectrométrie Nucléaire et de Spectrométrie de Masse, CNRS-IN2P3, Bâtiment 108, F-91405 Campus Orsay, France Françoise Yiou 1Centre de Spectrométrie Nucléaire et de Spectrométrie de Masse, CNRS-IN2P3, Bâtiment 108, F-91405 Campus Orsay, France B. Clark Burchfiel 2Department of Earth, Atmospheric and Planetary Sciences, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 Peter Molnar 2Department of Earth, Atmospheric and Planetary Sciences, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 Deng Qidong 3Institute of Geology, State Seismology Bureau, Beijing, China Li Jun 4Provincial Bureau of Seismology, State Seismology Bureau, Urumqi, Xinjiang, China Publisher: Geological Society of America First Online: 01 Jun 2017 Online ISSN: 1943-2674 Print ISSN: 0016-7606 Geological Society of America GSA Bulletin (1998) 110 (3): 377–386. https://doi.org/10.1130/0016-7606(1998)110<0377:EOSRIT>2.3.CO;2 Article history First Online: 01 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 Erik Thorson Brown, Didier L. Bourlés, Grant M. Raisbeck, Françoise Yiou, B. Clark Burchfiel, Peter Molnar, Deng Qidong, Li Jun; Estimation of slip rates in the southern Tien Shan using cosmic ray exposure dates of abandoned alluvial fans. GSA Bulletin 1998;; 110 (3): 377–386. doi: https://doi.org/10.1130/0016-7606(1998)110<0377:EOSRIT>2.3.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 SocietyGSA Bulletin Search Advanced Search Abstract Cosmic ray exposure dates (based on in situ–produced 10Be), in combination with measured heights of fault scarps that cut three abandoned fans, imply a slip rate of less than ∼2 mm/yr on the bounding thrust fault along a segment of the southern flank of the Tien Shan of central Asia. This rate, somewhat lower than those for the segment farther west and for the northern margin of the belt, implies that the distribution of shortening across the Tien Shan must change markedly along the belt. The date of abandonment of the smallest of the three fans is consistent with fan formation since the last glacial maximum, but the other two fans appear to have been formed and abandoned prior to that time. These and other results suggest that advances and retreats of alpine glaciers may not be synchronized with continental ice sheets and that not all prominent geomorphological features in arid Asian regions have formed since the last glacial maximum.In this study we have assessed the relationship between cosmogenic nuclide content of individual clasts and the time since their deposition on a surface. Cosmogenic nuclide accumulation represents the integrated total surface exposure of rocks in source regions during transport and since deposition. Postdepositional processes (erosion, burial, bioturbation, and cryoturbation), all of which decrease the quantity of cosmogenic nuclides produced in a rock in a given time and hence the apparent exposure age, also cause significant scatter among apparent ages of samples from the surfaces. Very low 10Be concentrations in material from active streambeds and at depth below one of the fan surfaces indicate that exposure prior to deposition onto fan surfaces was minimal (<∼2000 yr); it follows that the dates for individual clasts are lower limits for the time since abandonment of the fans. Because such dates place lower bounds on the time since initiation of scarp preservation, the associated slip rates should represent upper limits. 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.