Quaternary Stratigraphy of the La Playa Archaeological Site (SON F:10:3), Northern Sonora, Mexico - Reconstructing Human-Landscape Interactions: Interpreting Desert and Fluvial Environments - page 3

Quaternary Stratigraphy of the La Playa
Archaeological Site (SON F:10:3),
Northern Sonora, Mexico

Brett T. McLaurin, Aileen C. Elliott, James T. Watson
and Maria Elisa Villalpando Canchola

Abstract The La Playa archaeological site is located along the Rio Boquillas, north
of Trincheras in northern Sonora, Mexico. The site contains an extensive record of
human occupation beginning during the Paleoindian period with the most intense
utilization of the site during the Early Agricultural period (3,700-1,900 cal BP).
This work focused on detailed mapping and description of the stratigraphic units
across the site. The oldest exposed stratigraphic unit is a reddish, sandy paleosol. The
paleosol grades laterally into gravels that contain cobble-size clasts of diverse
compositions. Overlying the paleosol is a tan-brown, homogenous silt (Holocene?)
that lacks sedimentary structures and is consistently 98% silt and clay and 2% very
fine sand. The paleosol and associated gravels were deposited during relatively wet
conditions. The gravels are evidence of alluvial channels traversing the landscape
and the composition of these gravels indicates significant transport distance based on
the occurrence of nonlocal lithologies. The paleoenvironmental interpretation for the
overlying silt has been considered a cienega deposit, but the silt has many charac-
teristics in common with eolian deposited loess. An alluvial floodplain interpretation