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Calibration of the in situ cosmogenic 14C production rate in New Zealand's Southern Alps

In situ cosmogenic 14C (in situ 14C) analysis from quartz‐bearing rocks is a novel isotopic tool useful for quantifying recent surface exposure histories (up to ∼25 ka). It is particularly powerful when combined with longer‐lived cosmogenic isotopes such as 10Be. Recent advances in the extraction of in situ 14C from quartz now permit the routine application of this method. However, only a few experiments to calibrate the production rate of in situ 14C in quartz have been published to date. Here, we present a new in situ 14C production rate estimate derived from a well‐dated debris flow deposit in the Southern Alps, New Zealand, previously used to calibrate 10Be production rates. For example, based on a geomagnetic implementation of the Lal/Stone scaling scheme we derive a spallogenic production rate of 11.4 ± 0.9 atoms 14C (g quartz)−1 a−1 and a 14C/10Be spallogenic production rate ratio of 3.0 ± 0.2. The results are comparable with production rates from previous calibrations in the northern hemisphere. Copyright © 2012 John Wiley & Sons, Ltd.