2.2. Bute Inlet turbidity current system
Downstream of the Homathko and Southgate Deltas lie two submarine channels, which merge into a single sinuous channel formed by turbidity currents (Prior et al., 1986, 1987; Fig. 3). The channel is incised into the seafloor to a depth of up to 55 m. The channel floor is flanked by terraces that are particularly well-developed in the first 10 km of the fjord. Further downstream (430-580 m water depth) the submarine channel becomes less incised and is flanked by levees that are variably developed (Prior et al. 1987). For simplicity, in this paper we use the term “overbanks” to describe both the muddy terraces and levees bounding the submarine channel floor in Bute Inlet along its entire length.
The sediment composition of the Bute Inlet turbidity current system has been described in older work, based on sediment cores (Prior et al., 1986, Zeng et al., 1991), yet the OC composition of these cores was not documented until recently. The OC stored within the submarine channel floor was shown to be composed mostly of young terrestrial woody debris buried within fine sands (Hage et al., 2020). In this study, we build on the findings of Hage et al. (2020) from the channel floor, by documenting the distribution of OC across all of the sub-environments within this turbidity current system (i.e. channel floor, overbanks, lobe and distal flat basin). We also build on previous work on repeated bathymetric surveys and core dating (Heijnen et al., in review; Syvitski et al., 1988) to derive sedimentation rates and OC burial fluxes across the fjord.
3. Materials and Methods