Measurement Background and the Sediment Age-Dating Reach of 32Si

Silicon-32 can fill the sediment geochronology gap between 210Pb (1000 years). However, detector sensitivity and purification challenges of 32Si have limited the number of 32Si sediment dating studies. Targeting the intermediate age between 100 and 1000 years can provide geochronological reconstructions of paleoindicators that identify recent human and climate-induced shifts in coastal areas. We are currently preparing new detectors and kilogram-scale sample preparation techniques for such a study of Puget Sound sediments. This work considers the impact of detector background on counting time and the 32Si age-dating reach. Design and initial performance of new low-background, gas-proportional beta counters to measure 32Si (via 32P) are discussed.