Submarine fan channels and levees
The canyons that incise into the shelf edge funnel
sediment and water to discrete points at the edge of
the ocean basin where turbidity currents flowing
down the canyons pass into channels. Unlike the
canyons, the channels are not incised into bedrock,
but may scour into underlying submarine fan deposits
(Fig. 16.4). Submarine fan channels are variable in
size: some of the larger modern examples are several
tens of kilometres wide and over a thousand metres
deep, and in the stratigraphic record there are submarine
fan channels with thicknesses of up to 170m
and 20 km across (Macdonald & Butterworth 1990).
The deposits in the channel are typically coarse sands
and gravel that form thick, structureless or crudely
graded beds characterised by Tab of the Bouma
sequence and S1–3 of the ‘Lowe-type’ high-density
turbidite model (4.5.2). The lateral extent of these
turbidite beds is limited by the width of the channel,
which, when it is filled, forms a lenticular body made
up of stacked coarse-grained turbidites.