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