CHEMICAL ENRICHMENT OF SOILS AT ARCHAEOLOGICAL SITES: SOME OREGON CASE STUDIES

Abstract

Soil samples from six sites were analyzed for pH and total P, Ca, Mg, K, Na, Fe, and Mn. P is the most widely used chemical indicator of prehistoric human occupancy of a site, but other elements help in interpreting specific archaeological features within a site. Soil enrichment in P varies with the intensity of prehistoric occupancy of a site. Transient camps show little chemical enrichment, and intensely-occupied residential sites show strong enrichment in P, particularly around hearths and other areas where food or human wastes were deposited. Samples with high P concentrations commonly are also enriched in Ca and Mn. Features with bone are commonly enriched in other bases and Fe. Use of multiple elements allows identification of non-bone waste areas, waste areas with bone, burials with bone which are not waste areas, and non-cultural features such as natural charcoal concentrations. Vertical profiles are chemically stratified at 10-cm levels, and stratification is closely related to archaeological features. [Key words: soils, archaeology, soil chemistry, Oregon.]