LATE PLEISTOCENE HUMAN OCCUPATION OF THE BIGHORN MOUNTAINS

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With National Science Foundation funding, Dr. Robert Kelly will investigate late Pleistocene deposits in rockshelters in Wyoming's Bighorn Mountains. Some of the earliest artifacts in North America are fluted points; these are associated with what many archaeologists believe to the initial colonization of North American, and date from about 12,000 to 13,500 years ago, the late Pleistocene period. Unlike later peoples of North America, makers of fluted points seem to have rarely used cave and rockshelters. In their colonization model, Robert Kelly and Lawrence Todd (1988) argued that this fact indicated that flute point makers did not use "rare" landscape elements because they were part of a rapid colonization of North America. However, infrequent occurrence of fluted points in shelters could be a sampling problem (e.g, failure to excavate deep enough), or a result of shelter taphonomy (e.g, shelters that are currently observable were uninhabitable in the late Pleistocene). Analysis of data from the U.S. suggests that fluted point occupations in caves and rockshelters are indeed rare, = 10% of sites with appropriately-aged deposits. But understanding how rare such occupations are in a given region is essential to understanding why they are rare. This projects aims to answer two questions for the Bighorn Mountains: have we adequately sampled 12,000-13,500 BP deposits in caves and rockshelters? and (b) what role, if any, does site taphonomy, processes involved in the geologic formation of the shelter or cave itself and its trapped sediments, play in conditioning the current lack of fluted point-aged occupations in caves and rockshelters? This project will investigate a series of shelters from a database of 150 in Wyoming's Bighorn Mountains; currently, only 3-4 of these can demonstrate archaeological penetration into pre-12,000 year old sediments, and only two contain fluted points. The goal is to test the 10% frequency generated from national data by adequately testing at least 30 shelters for 12,000 to 13,500 year old deposits. One must be able to demonstrate for these 30 shelters that shelter taphonomy is not an issue, that is, that the shelter was available for habitation and habitable. The investigators therefore are re-investigating previously excavated shelters, redating stratigraphic profiles through AMS and OSL dating procedures. With the assistance of two geoarchaeologists the team will also collect data relevant to evaluating each shelter's taphomic history. The researchers will also conduct test excavations in new shelters to ensure that an adequate sample of shelters in different types of bedrock and in different geologic settings (e.g. high vs. low elevation) are available. Intellectual MeritsOnce completed, this project will (a) establish for the first time, the frequency of fluted point occupations in shelters in a specific region; (b) evaluate the probability that sample bias and shelter taphonomy are responsible for the lack of fluted points in shelters; and (c) provide data to evaluate one piece of evidence used to support the Kelly/Todd late Pleistocene colonization model. Broader ImpactsIn 2003, the University of Wyoming initiated a new doctoral program in paleoindian archaeology; this project will provide training for students in that program; in addition, international students will participate (in 2005, from Russia). The data gathered will be useful to other research projects on the archaeology of the Bighorn Mountains. The project will interest a broad range of archaeologists researching early "paleoindian" archaeology throughout the Americas and, as such, strengthen the University of Wyoming's existing cooperative agreements with Russian and Argentine institutions.