The Origin of Tan Ashy Lenses in a Puget Sound Shell Midden: Results of Sediment Analysis

Excavation of a shell midden in Puget Sound, Washington, (45-SK-144) revealed tan-colored lenses full of shell fragments with an ashy feel, alternating with black lenses with abundant charcoal. Magnetic susceptibility tests. Curie tests, particle size and constituent analysis were performed to compare the two types of lenses and to determine the origin of the tan-colored samples. Sorting of the Strongylocentrotus spp. framents, while the black samples had a greater abundance of charcoal, bone, Saxidomus spp., and Mytilus edulis. The tan-colored lenses contained far less charcoal, but had higher magnetic susceptibility values (X0) than the black samples and contained magnetite, indicating that they are a product of burning. The differences between samples indicate tan samples were burned for longer durations or with greater intensity than black samples. Differences in shell types and clear boundaries between layers suggests they were burned at different times and possibly for different reasons.