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Sand & Bedrock Erosion

Origin of sand and bedrock erosion rates, Calvert Island

Sand is an important substrate of the near-shore marine ecosystem in coastal British Columbia, but exactly where does it come from? Sources for the sand include reworking of glacially-derived sediments from the last glaciation or erosion of contemporary bedrock in coastal settings. We propose to examine the provenance and production rate of Calvert Island sand. Geochemical and trace isotope geochemistry will allow us to fingerprint beach and shallow-marine sand; we will compare these data to geochemistry of representative samples collected from bedrock, glacial deposits both on Calvert Island and in regions to the east of Calvert, the source for the Cordilleran Ice Sheet. Terrestrial cosmogenic dating (10Be and 14C) for bedrock and regolith exposed on Calvert Island will allow us to estimate bedrock erosion rates for the last 14,000 years. The results of our study will help address the fundamental objectives proposed for the sandy ecosystems study; our investigation will also complement ongoing research of the Kwakshua Watersheds Program. More broadly, our study will better quantify natural rates of sediment supply to sandy ecosystems of British Columbia.

Sediment coring in inland lake using submersible vibracoring system.

Location of bedrock samples (data courtesy of the Geological Survey of Canada) processed for geochemistry.