Dating sediments from Paleoindian sites: The chronology of the earliest human migrants to the New World is still disputed and unevenly documented. Radiocarbon dating from well stratified sites has been the traditional means of assessing this chronology, but radiocarbon in many cases can have problems with contamination or lack of association between dated and target events. Luminescence provides a complementary methodology in not only providing an independent means of dating but also allowing evaluation of stratigraphic integrity. Luminescence dating of single grains has the potential to identify post-depositional mixing and other stratigraphic puzzles. We have applied single-grain dating to Paleoindian sites from the Southern High Plains of Texas and New Mexico, at Cactus Hill in Virginia, in central Alaska, and in northern Sonora. We are also involved in dating sand dunes in the “ice-free corridor” in Alberta.
Dating of ceramics and fire-modified rock: The ability to date directly the manufacture of ceramics by luminescence has many benefits in resolving chronological problems for ceramic-bearing cultures. Our laboratory routinely processes 100-200 ceramics per year. We have tried to identify dating problems that are particularly suited to luminescence but difficult to resolve by other methods. These include (1) dating small, surface sites lacking diagnostic artifacts but important for understanding settlement dynamics and land use, (2) determining the duration of occupation at sites, (3) identifying mixing of artifacts of different ages in the same location, (4) understanding the tempo of ceramic technological changes. This work was funded by NSF in the past, but is continuing with the multitude of contract work. We typically apply OSL and IRSL, as well as TL, for measuring luminescence on ceramics, and part of our research is to understand the behavior in ceramics of these different signals.
Dating architectural construction: We are exploring the potential of luminescence to date construction episodes of prehistoric architecture. We have in the past dated construction materials such as bricks and mortar. But we have also tried to date paleo-surfaces beneath architectural remains in order to estimate when the architecture was put there. This relies on the ability of luminescence to date paleosols to the time of their burial. Grains in active soils become exposed to sunshine by cycling to the surface via turbation. This process effectively ends with the placement of something over the surface, so that by dating the youngest grains in the paleosol, luminescence should be able to estimate the date of the placement. We initially applied this principle to dating the construction of earthen mounds in the Southeast. We are currently involved in a NSF-funded project to date the placement of rocks in “tipi rings” and other anthropogenic rock arrangements in the Rocky Mountains and Great Plains. To make the data assessable, we have provided links to various data files.