Submarine Slide and Slump Complexes, Exmouth Plateau, NW Shelf of Australia

Analysis of 3D seismic data shows that the Neogene to
near seabed section along the NW flank of the Exmouth
Plateau Arch has been affected by numerous slope failures.
Seabed collapses originated at water depths of ~1000 m
and extend down dip to depths well in excess of 1500 m. A
wide spectrum of slope failures have been identified, from
coherent slides, incoherent slumps to mass flow deposits, the
product of debris-flows and turbidity currents.
The slides in the study area are characterized by proximal
slide fault block systems that are expressed at the seafloor as
extensional ridges up to 500 m wide and 1 km long. The
up-dip extension is matched by down-dip toe thrusts. The
downslope toe is characterized by imbricate thrusts with
fault-related folds that form a prominent fold belt at the
seabed. The over-thickened leading edge of the toe-thrust
systems commonly has undergone gravitational collapse
resulting in second-order toe slides detached at shallower
stratigraphic levels.
Slump systems are characterized by contorted seismic
facies that rest on top of erosive basal shear surfaces that are
typically strongly striated. These striations are commonly
arranged in multiple crosscutting sets. Detailed analysis of
the orientation and crosscutting relationships of these sets
suggests a complex multi-stage evolution of slumps.
Progressive down slope disaggregation at the leading edge
of slumps promoted the development of mass flows. These
are characterised by strongly erosive canyons that link slumps
to down dip debris flow and turbidite fans.
The results of this work broaden our knowledge of the
distribution and characteristic of slope failure in the Exmouth
Plateau and shows that multiple slope processes can develop
and coexist within a single event and hence produce a final
composite failure.