Cosmogenic 3He age estimates of Plio-Pleistocene alluvial-fan surfaces in the Lower Colorado River Corridor, Arizona, USA

Cassandra R. Fenton, Jon D. Pelletier

Research output: Contribution to journalArticle

7 Scopus citations

Abstract

Plio-Pleistocene deposits of the Lower Colorado River (LCR) and tributary alluvial fans emanating from the Black Mountains near Golden Shores, Arizona record six cycles of Late Cenozoic aggradation and incision of the LCR and its adjacent alluvial fans. Cosmogenic 3He (3Hec) ages of basalt boulders on fan terraces yield age ranges of: 3.3-2.2Ma, 2.2-1.1Ma, 1.1Ma to 110ka, <350ka, <150ka, and <63ka. T1 and Q1 fans are especially significant, because they overlie Bullhead Alluvium, i.e. the first alluvial deposit of the LCR since its inception ca. 4.2Ma. 3Hec data suggest that the LCR began downcutting into the Bullhead Alluvium as early as 3.3Ma and as late as 2.2Ma. Younger Q2a to Q4 fans very broadly correlate in number and age with alluvial terraces elsewhere in the southwestern USA. Large uncertainties in 3Hec ages preclude a temporal link between the genesis of the Black Mountain fans and specific climate transitions. Fan-terrace morphology and the absence of significant Plio-Quaternary faulting in the area, however, indicate regional, episodic increases in sediment supply, and that climate change has possibly played a role in Late Cenozoic piedmont and valley-floor aggradation in the LCR valley.

Original languageEnglish (US)
Pages (from-to)86-99
Number of pages14
JournalQuaternary Research (United States)
Volume79
Issue number1
DOIs
StatePublished - Jan 1 2013

Keywords

  • Basalt
  • Climate change
  • Colorado River
  • Cosmogenic He
  • Desert alluvial fans
  • Desert pavement
  • Southwest USA geomorphology
  • Surface exposure ages

ASJC Scopus subject areas

  • Arts and Humanities (miscellaneous)
  • Earth-Surface Processes
  • Earth and Planetary Sciences(all)

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