In our column in May, we discussed prehistoric use of the upper Bridge River by St’át’imc peoples and the volcanic eruption of Mount Meager that covered the valley in blankets of Bridge River Ash approximately 2,400 years ago.
As described in the last column, scatters of stone artifacts are abundant along the Downton Reservoir in the upper Bridge River Valley. However, the sites are out of context, making it difficult to distinguish between sites used before and after the Mount Meager eruption. While habitation sites (such as the Bridge River village) are absent in the middle and upper Bridge River Valley archaeological record, diagnostic tools and lithic scatters provide indicators on how and when this resource rich landscape was used and occupied.
A short distance downstream from the Downton Reservoir is the Carpenter Reservoir, stretching from near the town of Goldbridge to approximately 47 kilometres downstream to the Terzaghi Dam. Similar to the Downton Reservoir, Carpenter Reservoir is covered by Bridge River volcanic ash, though the ash deposits are not as thick as the deposits observed farther upstream.
Archaeological surveys over the last few years by St’át’imc Government Services (SGS) have found frequent scatters of stone artifacts along both banks of the reservoir. Volcanic ash layers can be useful for archaeologists, as archaeological sites occurring below ash layers can be confidently determined to be older than the eruption, while those above the ash layer are more recent. The changing environment of reservoirs make this impossible, as the ash tends to move up and down in the water column and collect on low-lying lands at high pool.
Unlike sites we described at the Downton Reservoir, several archaeological sites found during surveys of the Carpenter Reservoir included temporally diagnostic artifacts. The method of relative dating stone tools has been discussed in previous Dig It columns, but as a refresher, based on stylistic attributes, certain tools and points can be associated with specific dates as “horizon markers” by comparing them to other projectile points found in dateable contexts (like systematic investigations with secure carbon dates).
So far, dateable artifacts found along the Carpenter Reservoir can be assigned to time periods between 3,500 and 200 years before present.
At one archaeological site that is densely packed with stone artifacts, projectile points from the Shuswap Horizon (3,500-2,400), the Plateau Horizon (2,400-1,200) and the Kamloops Horizon (1,200-200) were found scattered on the surface amidst drifts of volcanic ash. At another site a bit further downstream in the reservoir, six diagnostic projectile points were identified that span the same time periods, and a third site includes points from 3,500-1,200 years before present.
Projectile point styles don’t change overnight, and while we can’t be certain of how long after the Mount Meager eruption it took for people to return to the middle Bridge River, it’s clear that particular locations were well used before and after the eruption. Due to the exposed nature of the reservoir, secure carbon-dating samples would be difficult to find. Future investigations will hopefully discover archaeological sites in undisturbed contexts outside of the exposed reservoir, where we can determine depths of artifacts relative to the volcanic ash (buried below the ash means older, whereas above the ash means more recent) or collect secure dating samples.
Archaeological sites can represent a single-use occupation, or repeated and continual use of a landscape over time. Based on the artifacts found in the upper and middle Bridge River Valley, it’s clear this landscape was subject to continual use by St’át’imc for millennia.
As we encounter our own modern catastrophic climate events, it’s useful to remember that humans have survived past devastating events and thrived, but they did so out of necessity, whereas we have choices.
Alysha Edwards is a St’át’imc archaeologist and graduate student at the University of Montana. Matt Begg is an archaeologist based in Kamloops.