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Chronology and Ecology of Late Pleistocene Megafauna in the Northern Willamette Valley, Oregon

Published online by Cambridge University Press:  20 January 2017

Daniel M. Gilmour*
Willamette Cultural Resources Associates, Ltd., 623 SE Mill Street, Portland, OR 97214, USA Department of Anthropology, Portland State University, P.O. Box 751, Portland, OR 97202, USA
Virginia L. Butler
Department of Anthropology, Portland State University, P.O. Box 751, Portland, OR 97202, USA
Jim E. O'Connor
U.S. Geological Survey, 2130 SW 5th Avenue, Portland, OR 97201, USA
Edward Byrd Davis
Museum of Natural and Cultural History, University of Oregon, 1680 E. 15th Ave., Eugene, OR 97403, USA Department of Geological Sciences, 1272 University of Oregon, Eugene, OR 97403, USA
Brendan J. Culleton
Department of Anthropology, Pennsylvania State University, 409 Carpenter Building, University Park, PA 16802, USA
Douglas J. Kennett
Department of Anthropology, Pennsylvania State University, 409 Carpenter Building, University Park, PA 16802, USA
Gregory Hodgins
NSF-Arizona AMS Facility, Department of Physics, University of Arizona, Physics Building, 1118 East Fourth St., P.O. Box 210081, Tucson, AZ 85721, USA School of Anthropology, University of Arizona, USA
*Corresponding author. E-mail (D.M. Gilmour), (V.L. Butler), (J.E. O'Connor), (E.B. Davis), (B.J. Culleton), (D.J. Kennett), (G. Hodgins).


Since the mid-19th century, western Oregon's Willamette Valley has been a source of remains from a wide variety of extinct megafauna. Few of these have been previously described or dated, but new chronologic and isotopic analyses in conjunction with updated evaluations of stratigraphic context provide substantial new information on the species present, timing of losses, and paleoenvironmental conditions. Using subfossil material from the northern valley, we use AMS radiocarbon dating, stable isotope (δ13C and δ15N) analyses, and taxonomic dietary specialization and habitat preferences to reconstruct environments and to develop a local chronology of events that we then compare with continental and regional archaeological and paleoenvironmental data. Analysis of twelve bone specimens demonstrates the presence of bison, mammoth, horse, sloth, and mastodon from ~ 15,000–13,000 cal yr BP. The latest ages coincide with changing regional climate corresponding to the onset of the Younger Dryas. It is suggested that cooling conditions led to increased forest cover, and along with river aggradation, reduced the area of preferred habitat for the larger bodied herbivores, which contributed to the demise of local megafauna. Archaeological evidence for megafauna–human interactions in the Pacific Northwest is scarce, limiting our ability to address the human role in causing extinction.

Research Article
University of Washington

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