TY - JOUR
T1 - Cosmogenic nuclide data sets from the Sierra Nevada, California, for assessment of nuclide production models
T2 - II. Sample sites and evaluation
AU - Phillips, Fred M.
AU - Hinz, Michelle
AU - Marrero, Shasta M.
AU - Nishiizumi, Kunihiko
PY - 2016/10/1
Y1 - 2016/10/1
N2 - The Cosmic-Ray Produced Nuclide Systematics on Earth Project (CRONUS-Earth Project) has reused a limited number of ‘legacy’ 10Be, 26Al, and 36Cl samples of latest Pleistocene age for the assessment of cosmogenic nuclide production rates independently derived by the CRONUS-Earth Project. The studies re-evaluated here include ones from the Sierra Nevada, California, originally measured by Nishiizumi et al. (1986), Evans et al. (1997), and Phillips et al. (2009). We have also analyzed a limited number of new samples from the same area. We have reevaluated the geological context of the legacy samples, their chronological controls, and the consistency of the data. The locations and settings of the 1986 samples for 10Be and 26Al calibration can be verified to within reasonable degree of precision using comparison of published locations and field photos with Google Earth imagery. Two cosmogenic sites, Greenstone Lake and Baboon Lakes, were also the localities where key 14C samples for glacial chronology were collected, giving confidence in the application of the 14C constraints to the cosmogenic nuclide samples. A considerable amount of more distant radiocarbon dating work supports an age of 15,750 ± 500 years for the exposure of the cosmogenic calibration samples associated with the Tioga 4 glacial retreat. These samples do all appear to be on surfaces that were exposed by final Tioga glacier retreat (15,750 ± 500 years), but below the limits of the Recess Peak advance (13,550–13,050 years). The 36Cl samples reported by Phillips et al. (2009) and Evans et al. (1997) were from the terminal moraine of the last Tioga glacier advance (16,100 ± 500 years), the final Tioga glacier retreat (15,750 ± 500 years), and the Recess Peak glacial episode (13,300 ± 250 years). When ages are calculated for these samples using the final CRONUS-Earth Project production rates and scaling models, they are in good agreement with the independent radiocarbon age control, with the exception of the 36Cl ages from the Recess Peak episode, which average about 15% young. The most likely reasons for this discrepancy are either inadequate understanding of snow shielding or error in the assignment of the age of the Recess Peak glacial advance.
AB - The Cosmic-Ray Produced Nuclide Systematics on Earth Project (CRONUS-Earth Project) has reused a limited number of ‘legacy’ 10Be, 26Al, and 36Cl samples of latest Pleistocene age for the assessment of cosmogenic nuclide production rates independently derived by the CRONUS-Earth Project. The studies re-evaluated here include ones from the Sierra Nevada, California, originally measured by Nishiizumi et al. (1986), Evans et al. (1997), and Phillips et al. (2009). We have also analyzed a limited number of new samples from the same area. We have reevaluated the geological context of the legacy samples, their chronological controls, and the consistency of the data. The locations and settings of the 1986 samples for 10Be and 26Al calibration can be verified to within reasonable degree of precision using comparison of published locations and field photos with Google Earth imagery. Two cosmogenic sites, Greenstone Lake and Baboon Lakes, were also the localities where key 14C samples for glacial chronology were collected, giving confidence in the application of the 14C constraints to the cosmogenic nuclide samples. A considerable amount of more distant radiocarbon dating work supports an age of 15,750 ± 500 years for the exposure of the cosmogenic calibration samples associated with the Tioga 4 glacial retreat. These samples do all appear to be on surfaces that were exposed by final Tioga glacier retreat (15,750 ± 500 years), but below the limits of the Recess Peak advance (13,550–13,050 years). The 36Cl samples reported by Phillips et al. (2009) and Evans et al. (1997) were from the terminal moraine of the last Tioga glacier advance (16,100 ± 500 years), the final Tioga glacier retreat (15,750 ± 500 years), and the Recess Peak glacial episode (13,300 ± 250 years). When ages are calculated for these samples using the final CRONUS-Earth Project production rates and scaling models, they are in good agreement with the independent radiocarbon age control, with the exception of the 36Cl ages from the Recess Peak episode, which average about 15% young. The most likely reasons for this discrepancy are either inadequate understanding of snow shielding or error in the assignment of the age of the Recess Peak glacial advance.
KW - Aluminum-26
KW - Beryllium-10
KW - Chlorine-36
KW - Cosmogenic nuclide production rate
KW - Glacial chronology
KW - Sierra Nevada
UR - http://www.scopus.com/inward/record.url?scp=84955602821&partnerID=8YFLogxK
U2 - 10.1016/j.quageo.2016.01.003
DO - 10.1016/j.quageo.2016.01.003
M3 - Article
AN - SCOPUS:84955602821
SN - 1871-1014
VL - 35
SP - 101
EP - 118
JO - Quaternary Geochronology
JF - Quaternary Geochronology
ER -