Measurement background and the sediment age-dating reach of 32Si

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