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

Detector sensitivity and purification challenges have limited published 32 Si sediment dating studies. The cosmogenic isotope 32 Si can fill the sediment geochronology gap between 210 Pb (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 32 Si age-dating reach. Design and performance of new low-background, gas-proportional beta counters to measure 32 Si (via 32 P) are discussed.