AN ABSTRACT OF THE THESIS OF Jennifer J. Thatcher for the degree of Master of Arts in Interdisciplinary Studies in Anthropology. Anthropology, and Geography presented on December 8. 2000. Title: The Distribution of Geologic and Artifact Obsidian from the Silver Lake/Sycan Marsh Geochemical Source Group. South-Central Oregon. Redacted for Privacy Abstract approved: J. Roth Geochemical characterization methods are commonly used in the reconstruction of prehistoric raw material use and procurement systems. Trace element studies of lithic source material and artifacts, specifically those made of obsidian, can reveal important information about the environmental and cultural factors which influence the prehistoric distribution of raw material. The current investigation uses geochemical characterization methods and data to document and evaluate the distribution of geologic and artifact obsidian that originates from the Silver Lake/Sycan Marsh (SL/SM) obsidian source. This large and prehistorically significant source is located in western Lake County, Oregon. Few source descriptions or artifact distribution studies exist for SL/SM obsidian. However, over the past decade, a significant increase in the use of geochemical characterization methods has generated a wealth of data for Oregon obsidian sources. This thesis synthesizes the results of the geochemical characterization analysis of 392 geologic obsidian specimens collected from the SL/SM source area and 1,938 SL/SM obsidian artifacts recovered from over 200 archaeological sites in Oregon, Washington and California. The artifact analytical data were derived from previously characterized artifact collections compiled and archived in an extensive database. A subset of artifacts were characterized for the purpose of this study. Based on the results of geochemical analysis of the geologic material, two distinct source boundaries are defined for the SL/SM geochemical source. The trace element data show that the geologic SL/SM obsidian source material originates from two chemically- related obsidian domes which lie in separate drainage basins. Accordingly, this investigation establishes that the natural distribution of geologic obsidian is highly dependent upon the regional topography. Spatial analyses of the artifact obsidian demonstrate a widespread distribution of SL/SM obsidian throughout central and western Oregon and parts of northwest California and southwest Washington. Numerous cultural and environmental variables appear to have affected the artifact distribution at local and regional levels. The findings show a predominance of SL/SM artifact obsidian use along the western slopes of the Cascade Range within the southern half of Oregon. Locally, use of the source appears to be less pronounced due to the abundance of competing central and eastern Oregon obsidian sources. The results suggest that SL/SM artifact obsidian was distributed both intentionally and incidentally as a result of prehistoric procurement and exchange systems. ©Copyright by Jennifer J. Thatcher December 8, 2000 All Rights Reserved The Distribution of Geologic and Artifact Obsidian from the Silver Lake/Sycan Marsh Geochemical Source Group. South-Central Oregon by Jennifer J. Thatcher A THESIS submitted to Oregon State University in partial fulfillment of the requirements for the degree of Master of Arts in Interdisciplinary Studies Presented December 8, 2000 Commencement June, 2001 Master of Arts in Interdisciplinary Studies thesis of Jennifer J. Thatcherpresented on December 8, 2000 APPROVED: Redacted for Privacy Major Professor, representing Anthropology Redacted for Privacy Committee Member, representing Anthropology Redacted for Privacy Committee Mer6jer,represe ing Geography Redacted for Privacy Chair of D artment of Ant pol Redacted for Privacy Dean of Gra tè-School I understand that my thesis will become part of thepermanent collection of Oregon State University libraries. My signature below authorizes release ofmy thesis to any reader upon request. Redacted for Privacy Jetihifer J. Thatcher, Author ACKNOWLEDGMENTS I wish to express my sincere gratitude to my committee members: Barbara Roth, Craig Skinner, and Dawn Wright. They enthusiastically provided me with many helpful comments and suggestions. This thesis certainly would not have been possible without their guidance. In particular, I would like to extend my thanks to Craig Skinner, my mentor and friend of 10 years, for his immeasurable patience, generosity, and encouragement. He provided me with much needed advice on numerous occasions and was always available to address my endless questions and concerns. In addition to a steady stream of academic counsel, he contributed XRF analytical services, obsidian analytical data, field equipment, office space, employment, and countless mochas. He was instrumental inmy decision to return to school and pursue the topic of this thesis. I feel extremely fortunate to be affiliated with Craig and I am grateful to him for his constant support and unwavering faith. Many individuals contributed their time, comments, and data to this project. My deepest thanks go to: Mel Aikens, Isaac Barner, Pam Endzweig, Le Gilson, John Kaiser, and Brian O'Neill. Dennis Jenkins supplied several obsidian samples used in this research and was a wonderful host during a brief visit to the University of Oregon field school in 1998. Over the years, Dennis has engaged me in many entertaining and insightful conversations about Fort Rock prehistory and he is to be thanked for his input. Ann Rogers has been very generous in her support of this project. She provided literature sources, contact information, and several trips to the State Historic Preservation Office in Salem. Ann along with Debbie Johnson employed me at the Oregon State University Research Forests and graciously permitted me to keep a very flexible work schedule. Funding for XRF analysis of geologic samples used in this research was provided by the Association of Oregon Archaeologists and Northwest Research Obsidian Studies Laboratory. Financial assistance for the cost of tuition was provided by the Oregon Laurels Scholarship. Chris Coon, Jeff Merth, Brent Munkres, Arianna Ruder, and Kathie Thatcher have each accompanied me on field trips to the Silver Lake area. They donated their time, food, vehicles, powers of observation, love of adventure, and good humor in the pursuit of collecting geologic obsidian. I would like to thank friends and fellow graduate students Jun Kinoshita, Rebecca Snyder, and Michele Wilson for being there to endure the same frustrations, trials and tribulations. Michele, in particular, was always there to help me see things more clearly. Many other friends are to be thanked for their generosity, hospitality, and advice: Gary Bowyer, Shannen Chapman, Doug Harro, Marge Heizer, Becky McKim, Lou Ann Speulda, Jama Duckworth Williams, and Scott Williams. Special mention goes to Linda Audrain for teaching me the art of stress reduction through sock-knitting. On the order of inanimate objects, I'd like to thank Florence, the spectrometer, for never letting me down. I am exceptionally grateful for the love and encouragement of my family. Thanks to my grandmother and parents for always knowing what to say, to Tess and Brad for providing a home away from home, and to Ross and Ellie for reminding me that there is much more to life than school. And finally, to Jeff for being himself TABLE OF CONTENTS Page 1. iNTRODUCTION . 1 1.1 StudyArea.................................................2 1.2 Research Design.............................................3 1.3 Structure of the Thesis........................................6 2. ENVIRONMENTAL AND CULTURAL CONTEXT.......................7 2.1 Environmental Overview.......................................7 2.1.1 Physiography and Geology..............................7 2.1.2 Hydrology.........................................10 2.1.3 Climate............................................ 10 2.1.4 Flora..............................................11 2.1.5 Fauna............................................. 12 2.2 Ethnographic Overview....................................... 13 2.2.1 Tribal Distribution...................................14 2.2.2 Settlement and Subsistence Practices.....................17 2.3 Archaeological Overview.....................................21 2.3.1 Paleo-Climate.......................................22 2.3.2 Late Pleistocene/Early Holocene.........................22 2.3.3 Middle Holocene....................................25 2.3.4 Late Holocene......................................27 2.3.4.1 Middle Archaic............................... 27 2.3.4.2 LateArchaic.................................29 2.4 Summary..................................................30 3. THEORETICAL CONTEXT........................................31 3.1 Procurement and Exchange Systems.............................31 3.2 Characteristics of Procurement and Exchange Systems...............32 TABLE OF CONTENTS (Continued) Page 3.3 Variables Affecting the Spatial Distribution of Archaeological Obsidian.....................................37 3.3.1 Cultural Variables....................................38 3.3.1.1CulturalBoundaries...........................38 3.3.1.2Population Variables..........................39 3.3.1.3Cultural Preferences...........................40 3.3.1.4Site Function................................41 3.3.2 Environmental Variables...............................42 3.3.2.1Source Location..............................42