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Genesis of an Artifact Layer: Natural
and Cultural Processes at the La Playa
Archaeological Site, Sonora, Mexico
Aileen C. Elliott, Brett T. McLaurin, James T. Watson
and Maria Elisa Villalpando Canchola
Abstract The La Playa archaeological site (SON F:10:3), in Sonora, Mexico,
preserves 12,000 years of human utilization and occupation. Geologically, the site
is characterized by a homogenous silt (Holocene?) overlain in places by a thin
layer (2-6 cm) of cultural artifacts (ceramics and groundstone). This artifact layer
is overlain by interbedded silts and cross-laminated and rippled, sands. The goal of
the study was to map the distribution of the artifact layer and overlying sediments
to determine: (1) if the layer is a lag deposit resulting from deposition and
concentration of artifacts by fluvial processes; or (2) if it is a cultural layer and
represents an earlier occupation that was subsequently buried. Results show that
the artifact layer is confined to a 0.4 km 2 area of the site and dips to the southwest
at approximately 0.5, which is consistent with the slope of the current topographic
surface. The artifact layer is a cumulative palimpsest that reflects the mixing
and concentration of artifacts from multiple occupations. The artifact layer was
subsequently buried by sediments deposited by fluvial processes after A.D. 150 as
indicated by the presence of Trincheras period ceramics.
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