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Problems and prospects in the preservation of Late Pleistocene cultural sites in southern Oregon coastal river valleys: Implications for evaluating coastal migration routes

Early human migration into the New World is hypothesized to have occurred along the northwest coast of North America as early as the Late Pleistocene. Following initial coastal occupation, humans may have moved inland following coastal rivers where their sites would presumably be easier to find. However, evidence of such inland mobility is lacking. The paucity of early sites in coastal river valleys is due, in part, to the dynamic geomorphic evolution of the northwest coast landscape during and after the Late Pleistocene. Three case studies from the southern Oregon coast illustrate the complex relation between tectonics and geomorphic processes along an active margin coast, such as Oregon's Cascadia subduction zone. Local, upper‐plate tectonic structures play a major role in the preservation and accessibility of Pleistocene‐age stream terrace deposits and, in turn, the cultural deposits they may contain. A better understanding of the tectonogeomorphic setting of active margin coasts will allow archaeologists testing a coastal migration hypothesis to focus their efforts on landforms of the appropriate age on a subregional scale, such as the Oregon coast. © 2006 Wiley Periodicals, Inc.