Viable paleosol microorganisms, paleoclimatic reconstruction, and relative dating in archaeology: a test case from Hell Gap, Wyoming, USA

Living soil microorganisms are ubiquitous and could provide unrealized contributions to paleoenvironmental, dating, and other archaeological research. We evaluated the effectiveness of a previously proposed microbiological technique for paleoclimatic reconstruction (which has been applied but not adequately verified), and also introduced and tested a preliminary method of using soil microbe density for relative dating. Soils from a sample column representing a complete chronosequence at Hell Gap, Locality I, Wyoming, were cultured on three different solid media. To test the paleoclimatic reconstruction method, trophic group data were tested for serial correlation and compared to soil and phytolith analyses formerly completed at the site. Microbial trophic group composition significantly correlated to soil pH, but not to prior precipitation reconstructions. Further refinement is required before the paleoclimatic reconstruction method can be implemented with confidence. Additionally, microbial density decreased with age, suggesting a temporal signature within the sample column and that density could potentially be used as a relative dating technique.