Paleoenvironmental interpretation of the paleosols and sediments at the Stampede site (DjOn-26), Cypress Hills, Alberta

Abstract

A 3.65 m-thick sequence of paleosols and sediments exposed at the Stampede archaeological site provides an opportunity for studying climate change and its impact on ancient site utilization over a 7200-year period. Three radiocarbon dates establish temporal boundaries for the lower sequence of paleosols and sediments at 7200 and 6100 BP. This lower sequence is characterized by lack of cultural material in most paleosols, high accumulation rates, and evidence for fluvial deposition. The upper sequence dates from 6100 BP and is characterized by low accumulation rates, increased pedogenesis, and increased evidence for human occupation, particularily between 4660 and 5230 BP. Phytoliths provide a strong signal for grassland vegetation beginning at 6100 years BP coincident with the most intensive occupation of the site. Stable carbon isotopes and carbon/nitrogen (C/N) ratios support the presence of grass. The differences evident between the lower and upper sequences can be attributed to the change from warm dry conditions to cooler, moister conditions and agree to a first approximation with the information inferred from the nearby Elkwater Lake and Harris Lake records. However, the persistence of forest at the Stampede site for a 1400-year time interval, when the Harris Lake record indicates more arid conditions, suggests that springs and north-facing slopes made the Cypress Hills an "oasis" for both animals and people.