Thesis Scattered Glass: Obsidian Artifact
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THESIS SCATTERED GLASS: OBSIDIAN ARTIFACT PROVENANCE PATTERNS IN NORTHWESTERN WYOMING Submitted by Allison D. Bohn Department of Anthropology In partial fulfillment of the requirements For the Degree of Master of Arts Colorado State University Fort Collins, Colorado Spring 2007 COLORADO STATE UNIVERSITY February 28, 2007 WE HERBY RECOMMEND THAT THE THESIS PREPARED UNDER OUR SUPERVISION BY ALLISON DANIKA BOHN ENTITLED, SCATTERED GLASS: OBSIDIAN ARTIFACT PROVENANCE PATTERNS IN NORTHWESTERN WYOMING, BE ACCEPTED AS FULFILLING IN PART REQUIREMENTS FOR THE DEGREE OF MASTER OF ARTS. Committee on Graduate Work Robert O. Coleman Dr. Jason M. LaBelle Dr. Kathleen Galvin Advisor Dr. Lawrence C. Todd Department Head Dr. Kathleen Galvin ii Abstract of Thesis SCATTERED GLASS: OBSIDIAN ARTIFACT PROVENANCE PATTERNS IN NORTHWESTERN WYOMING Home to several high quality sources of the volcanic glass material, obsidian artifacts are found throughout the archaeological record in northwestern Wyoming. Obsidian is a useful lithic raw material for evaluating prehistoric land use patterns because it can be matched with the geochemical signatures of source materials. As part of the Greybull River Sustainable Landscape Ecology (GRSLE) project, this research seeks to evaluate obsidian distribution patterns in the Upper Greybull watershed and the relationship to local and regional land use patterns. The study area is located within the volcanically formed Absaroka Mountain range where there is clear evidence of prehistoric land use from the Late Paleoindian period to recent times. Field and laboratory components were conducted to evaluate several research questions. During the field component, artifacts were recorded following pedestrian surveys and a sample of obsidian artifacts were collected for geochemical characterization. The laboratory component consisted of the geochemical and lithic analysis of the sampled artifacts. Between 2002 and 2005, the GRSLE project recorded over 40,000 chipped stone artifacts from 166 sites and several isolated finds. Obsidian frequency is not uniform between the tributaries of the Upper Greybull and the material is most commonly found in the lower elevation ranges of the study area. Several varieties of raw material are available locally and regionally. Obsidian is a small portion of the total Greybull assemblage and artifacts are on average smaller than artifacts manufactured from other materials, indicating that obsidian is a highly curated raw material. The Late Prehistoric was the period of the most substantial obsidian use. iii A sample of 127 obsidian artifacts was sent for geochemical characterization and revealed an overwhelming propensity toward Obsidian Cliff obsidian. The other obsidian sources responsible for multiple artifacts include Bear Gulch, Teton Pass, and Malad. Teton Pass is approximately the same distance from the GRSLE study area as Obsidian Cliff, but was identified less often. Most projectile points are Late Prehistoric in age and are constructed of Obsidian Cliff obsidian. Late Archaic projectile points in the sample were not constructed of Obsidian Cliff material. Expedient artifacts such as debitage and worked flakes were associated with the more common sources, while rare source artifacts are primarily projectile points or bifaces. There was not a significant difference in artifact size between the source types. Spatial analysis of two sites revealed that parsing out singular obsidian procurement events is highly dependent on site complexity. Three obsidian interaction zones are identified using several published regional sites and study areas. The GRSLE study area is similar to sites and areas to the north and east, but temporal variability needs to be better understood to evaluate possible shifts in the pattern. Five land use scenarios have been developed to consider possible land use patterns through time. These include seasonal exploitation, montane adaptation, long range adaptation, foothills-basin adaptation, and stochastic acquisition. Seasonal exploitation is the most probable scenario indicated by the available data. The Absaroka Range poses physiographic barriers to importing Obsidian Cliff material into the GRSLE study area. Research along the Boulder Basin Pack Trail will further define the relationship of the GRSLE study area to regional land use patterns. Allison D. Bohn Anthropology Department Colorado State University Fort Collins, CO 80523 Spring 2007 iv Acknowledgements Between deciding a thesis topic, general grad school angst, being pregnant and giving birth, moving across the country and every other day-to-day roadblock, completion of this document has been a long time coming. Both Paul Burnett and Larry Todd helped develop the initial idea of this thesis in the spring of 2004 before heading in the field. Thank you to the many conference goers who have commented on my work and ideas along the way. The many graduate students, faculty and staff who provided emotional and professional support during my time at CSU are too many to mention all by name. Fellow grad students, Courtney Hurst, Marcy Reiser, Jill Bechberger, Chris Kinneer and Naomi Ollie helped with discussions, words of encouragement, and continued friendship. Terry Ritzman provided valued advice and friendship. Paul Burnett and Dr. Caryn Berg commented on drafts of this thesis. Dr. Kosha Bramesfeld gave her time to assist with some of the statistics in this paper. Without Larry Todd, my advisor, this thesis would not even have existed. Not only did he introduce me to the study area, but he provided the opportunity to spend two summers doing research I love in the most beautiful landscape I have ever seen. Also, the data herein are the property of the GRSLE project, run by Dr. Todd and I am forever indebted that I was granted this research opportunity! He has been a supportive advisor and a trusted friend. v Thank you to the rest of my committee, Jason, Rocky, and Kathy, for the valuable comments on my drafts and encouraging me to be a little more creative. Also thank you for working with me to schedule and reschedule meeting times and defense dates to accommodate the entire committee and my ever-changing life. While I occasionally think it was her who delayed the completion of this, it is Haven who has inspired me to keep going during the times when it seemed impossible. Both of my parents spent a week helping me by hanging out with Haven when Spike was not able and I needed to write. My sister, Rachel gave her assistance by reading the entire paper and editing for grammar. My husband Spike has been an integral part of this whole process including editing and brainstorming. Above all, he provided endless encouragement, opportunities for me to work, intellectual stimulation, warm meals, and the consistency of a happy and loving family. vi Table of Contents Abstract of Thesis .............................................................................................................. iii Acknowledgements............................................................................................................. v Table of Contents.............................................................................................................. vii List of Figures.................................................................................................................. viii List of Tables ..................................................................................................................... ix CHAPTER 1 Introduction ................................................................................................. 1 The Dynamic Greybull ................................................................................................... 8 Summary of Chapters ................................................................................................... 17 CHAPTER 2 Developing Analytical Frameworks........................................................... 18 Lithic Curation.............................................................................................................. 19 Moving Across Landscapes .......................................................................................... 21 Archaeological Indicators of Mobility.......................................................................... 26 Trade versus Transport ................................................................................................. 31 Lithic Analysis.............................................................................................................. 32 Chapter Summary ......................................................................................................... 38 CHAPTER 3 Obsidian Source Characterization ............................................................. 39 Process of Geochemical Characterization .................................................................... 42 Relevant Sources........................................................................................................... 44 Chapter Summary ......................................................................................................... 55 CHAPTER 4 Regional Obsidian Patterns ....................................................................... 56 Regional Sites ............................................................................................................... 57 Regional Studies ..........................................................................................................