GeoChemical Sourcing of LaPrele Mammoth Kill Ochre

Red ochre pigment, or the mineral hematite, is commonly recovered from Early Paleoindian sites in the American west. Although it is clear that early peoples in the New World were transporting pigments from place to place, the inability to date to determine ochre provenance has limited our understanding of the natural sources of ochre that were in use, as well as the distances over which ochre was transported. This work is a pilot study in sourcing of ochre from the La Prele Mammoth site, a 12,900 year old human occupation in Converse County, Wyoming. Excavations at this mammoth kill site have revealed a large area of hematite-stained sediments, and over 1,500 individual nodules of ochre were mapped and collected. As a first attempt to determine the provenance of the ochre from this site, I collected comparative geologic hematite samples from two well-known iron deposits in Wyoming, the Powars II site at the Sunrise Iron Mine near Hartville and the historic Rawlins red paint mine. I characterized each source chemically and mineralogically using ICP-OES and powder XRD, respectively. I found that the two sources can be differentiated and that the excavated ochre was found to most closely match that of the Powars II site, which occurs approximately 85 km down the valley of the Platte to the southeast. This study suggests different sources of red ochre are geochemically distinguishable and that provenance studies of ocher may become commonplace in Wyoming archaeology