Luminescence dating of sand deposits related to late Pleistocene human occupation at the Cactus Hill Site, Virginia, USA

Abstract

Optically stimulated luminescence (OSL) ages, obtained primarily using single grains, are reported for 13 sediment samples from the Cactus Hill site, a culturally stratified sand dune in Virginia. The site has drawn interest because of a blade level, potentially representing an early occupation of humans in North America, a few centimeters below a Clovis artifact layer. Pre-Clovis occupation in North America is disputed. Most of the ages are drawn from quartz grains, but the quartz at this site appears to saturate at a young age, so analysis on potassium feldspar grains was also performed on the deepest samples. Geologic evidence suggests deflation, small-scale turbation, and low accretion rates have compressed and slightly mixed some of the deposits. The diameters of OSL sampling tubes therefore cover long time spans for many samples, so a minimum age is determined statistically for the top of sampling volumes. The derived ages, with one exception, are in the correct stratigraphic order and are broadly in agreement with radiocarbon ages. This seems to confirm the overall integrity of the strata and places the deposit containing the pre-Clovis artifacts at about 18 ka. Further evaluation and constraint of the ages is provided by Bayesian analysis.