Journal of California and Great Basin Anthropology

The source direction of obsidian artifacts from archaeological contexts in Drews Valley, located on the northwestern Great Basin perimeter, provides evidence for an east-to-west shift in procurement or interaction spheres from Middle to Late Holocene times. For Elko and earlier periods, sources located to the northeast, in Oregon 's Chewaucan Basin, are predominant, and most of the remaining exotic obsidian is from other Great Basin sources, primarily from the Goose Lake basin to the southeast. Within the last ca. 1,300 years, sources on the Modoc Plateau to the southwest predominate, while sources in the Chewaucan and other easterly basins are rare. This shift, precipitated by a combination of factors that may have included environmental stress, conflict, and changing economic opportunities, may mark the initiation of the ethnographic pattern.