Extending Applications and Improving Methodology for Luminescence Dating of Archaeological Materials

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This award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5).Luminescence dating has become an increasingly useful chronological tool over the last couple of decades in archaeological and geological sciences. This is due to methodological developments and an increased perception that luminescence can provide dating information in contexts that other dating methods cannot. The luminescence laboratory at the University of Washington is one of the few that specializes in archaeological applications. With National Science Foundation support, the laboratory has explored a number of unique applications in the past and with new support plans to further this research in four areas.1) Throughout the western Great Plains and adjoining Rocky Mountains, prehistoric people have left a number of stone alignments -- some of which are the remnants of hunting drive lines or blinds, others of which had ritual functions ("medicine wheels"), and still others of which served as housing support ("tipi rings"). These alignments are ubiquitous but most have never been dated despite clear importance for understanding prehistoric settlement and subsistence in this region. The laboratory has done basic research in dating buried soils and will apply these methods to dating the sediments under the rocks to the time when the rocks were emplaced. Preliminary results show great promise and a dating program at several sites in Wyoming and Montana is being initiated, in collaboration with University of Arizona, Colorado State University and University of Quebec in Montreal.2) Luminescence has recently been applied to rock surfaces to date their last exposure to sunlight. As an exploratory project, the laboratory intends to see if the extent of light penetration into exposed rocks, as measured by their luminescence, can be used to date how long a rock has been exposed. This would allow dating when a building stone still exposed to sun was first cut, when lithic material in a quarry was last removed, or when prehistoric tools of sufficient size were flaked to form a finished tool. This work, using samples from a Colorado quarry, is in collaboration with a private technological firm in Colorado and with another luminescence laboratory in Scotland.3) The laboratory has been trying to perfect using optically stimulated luminescence (OSL) as an improved method for dating fine-grained prehistoric ceramics over the traditional thermoluminescence (TL). The laboratory has been applying pulsed OSL as a way to eliminate signal components which can lead to age underestimation, and will be undertaking analyses to better understand the pulsed signal in ceramics. This work is in collaboration with another laboratory in South Africa.4) The laboratory has a multi-year program dating paleoindian sites in Brazil as part of a larger project, in conjunction with the University of São Paulo, to better understand early human habitation in South America. The dating work has employed single-grain dating in an attempt to identify sediment mixing. Current research is aimed at better understanding how a date can be obtained from single grains.While this research is aimed at specific applications, the methodological developments can have much broader implications both for luminescence dating in general and for archaeology. All four areas of research can be applied in other areas of archaeology. The laboratory also serves an instructional role at the University of Washington and the current NSF support should provide a number of students with employment.