TY - JOUR
T1 - Cosmogenic 3He age estimates of Plio-Pleistocene alluvial-fan surfaces in the Lower Colorado River Corridor, Arizona, USA
AU - Fenton, Cassandra R.
AU - Pelletier, Jon D.
N1 - Funding Information:
We gratefully acknowledge field support and/or critical discussions with Leslie Hsu, Keith Howard, Kyle House, Phil Pearthree, and Brenda Buck. We thank Thure Cerling for use of the mass spectrometer at the University of Utah. Support was granted by the Gladys W. Cole Memorial Research Award received by C. Fenton in 2002 , the National Research Council (through a Research Associateship for Fenton 2002–2004), and the National Science Foundation award #0309518 to J.D.P. We wish to thank associate editor Jim Knox and two anonymous reviewers for their comments, which greatly improved the paper.
PY - 2013/1
Y1 - 2013/1
N2 - 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.
AB - 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.
KW - Basalt
KW - Climate change
KW - Colorado River
KW - Cosmogenic He
KW - Desert alluvial fans
KW - Desert pavement
KW - Southwest USA geomorphology
KW - Surface exposure ages
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U2 - 10.1016/j.yqres.2012.10.006
DO - 10.1016/j.yqres.2012.10.006
M3 - Article
AN - SCOPUS:84871508936
SN - 0033-5894
VL - 79
SP - 86
EP - 99
JO - Quaternary Research (United States)
JF - Quaternary Research (United States)
IS - 1
ER -