Sources and Transport of Surface Sediment and Metals in B.C. Fjord, Tahsis Inlet

Tahsis Inlet in Nootka Sound, British Columbia is a steep, narrow fjord with high tidal energy, a sidewall river delta, a mid-inlet passage to another fjord (Zeballos-Esperanza Inlet), and two rivers at its head. In this study 20 surface sediment samples were collected along its 39 km length. They were analyzed for grain size, loss on ignition, ⁷Be, and concentrations of 22 metals. Grain size distributions varied widely: very coarse (rocks, gravel, sand) around the sidewall delta to very fine (silt and clay) at both ends of the inlet. Principal Components Analysis (PCA) revealed distinct patterns of co-variation between metals, with Axis 1 explaining 55% of the variance and Axis 2 explaining 22% of the variance. Two major groupings of variables were created by these two axes. The Type I group consisted of D50, OC%, Ca, B, Si, S, Na, and K and were associated with marine-derived material. The Type II group consisted of Cu, Cr, Ni, Pb, Mo, Mg, Cd, Se, Al, and Fe and were associated with terrigenous material. High carbon isotope ratios of organic carbon, δ¹³C near the entrance of Zeballos Inlet was suggestive of a marine carbon source. Metal concentrations and ⁷Be patterns supported this interpretation. Enrichment factors relative to average shale were 600% for arsenic, 10,000% for cadmium, 9,000% for molybdenum, and 3,000,000% for selenium. These enrichments are attributed to local mining activities, physical transport via currents and landslide deposition.