HR: 13:55h
AN: U23B-02    [Abstracts]
TI: Calibration of Cosmogenic ³⁶Cl Production Rates from Holocene Lava Flows in Iceland
AU: * Denoncourt, C L
EM: cld2@cisunix.unh.edu
AF: Department of Earth Sciences, University of New Hampshire, Durham, NH 03824 United States
AU: Licciardi, J M
EM: joe.licciardi@unh.edu
AF: Department of Earth Sciences, University of New Hampshire, Durham, NH 03824 United States
AU: Stone, J O
EM: stone@geology.washington.edu
AF: Quaternary Research Center and Department of Earth and Space Sciences, University of Washington, Seattle, WA 98195 United States
AU: Finkel, R C
EM: finkel1@llnl.gov
AF: Center for Accelerator Mass Spectrometry, Lawrence Livermore National Laboratory, Livermore, CA 94550 United States
AU: Kurz, M D
EM: mkurz@whoi.edu
AF: Department of Marine Chemistry and Geochemistry, Woods Hole Oceanographic Institution, Woods Hole, MA 02543 United States
AB: We have measured cosmogenic ³⁶Cl concentrations in whole rock basalts from twenty-one calibration sites on four radiocarbon-dated postglacial lava flows in Iceland. The ³⁶Cl data were obtained from splits of rock from the same suite of calibration sites used to determine cosmogenic ³He production rates in recent work (J.M. Licciardi et al., submitted manuscript). These ³⁶Cl measurements allow a direct co-calibration between these two widely used cosmogenic isotopes. Preliminary results indicate that multiple calibration sites on individual lava flows yield ³⁶Cl production rates that agree within 1-sigma error, demonstrating strong coherency of the data. Mean ³⁶Cl production rates among the four lava flows are in reasonable agreement, with the exception of the youngest flow (Lambahraun) which yields notably higher production rates. The higher-than-average ³⁶Cl production rates from Lambahraun correspond with lower-than-average ³He production rates from this same flow, and may partly reflect the influence of snow cover. Production rates via the dominant Ca spallation pathway, which accounts for 60-70% of total ³⁶Cl production in the Iceland samples, are within the range of values reported in previous ³⁶Cl calibration studies. Additional ³⁶Cl measurements from the calibration sites are expected to allow a more detailed assessment of these preliminary findings. The new ³⁶Cl production rate calibrations will enable accurate ³⁶Cl surface exposure dating in Iceland.
DE: 1105 Quaternary geochronology
DE: 1150 Cosmogenic-nuclide exposure dating (4918)
DE: 1625 Geomorphology and weathering (0790, 1824, 1825, 1826, 1886)
SC: Union [U]
MN: Fall Meeting 2005