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A late Pleistocene (Marine Isotope Stage 5e) emergent marine sequence fringes the coastline of the Cape Region of coastal west central Australia and provides elevation and age control to characterize the locations and rates of crustal deformation. There is a systematic measurable change in relative paleo sea-level elevations across the Cape Region. High-precision leveling of modern and Pleistocene shoreline features indicates the minimum elevation range of MIS 5e shoreline features along the coast is 10.4 m. This compares with the 2.5 m elevation range for observed modern shoreline analogs. The lack of continuity of MIS 5e shoreline elevations along 300 km of coastline demonstrates continuing tectonic deformation along coastal anticlines in the Cape Region. Topographic expression of MIS 5e features indicates tectonic uplift consistent with late Neogene to Quaternary deformation on the Cape Cuvier and Cape Range anticlines. Post-MIS 5e tectonic uplift rates are up to 0.054 ± 0.035 mm/yr at fold axial locations. Estimated subsidence rates are − 0.013 ± 0.034 mm/yr on fold limbs. While the estimated vertical tectonic deformation is small and the rates are low, the geomorphological data also demonstrate tectonic activity, not stability.

3D exploration seismic data were interpreted to investigate the locations and characteristics of submarine slope failures along the continental slope in the offshore Carnarvon Basin on Australia’s North West Shelf. Seisnetics™, a patented genetic algorithm was used to process the 3D seismic data to extract virtually all trough and peak surfaces in an unbiased and automated manner. The extracted surfaces were combined in the 3D visual database to develop a seafloor digital terrain model that extends from the continental slope to the Exmouth Plateau. The 3D data were used to map the subsurface extent and geometry of landslide failure planes, as well as to estimate the thickness and volumes of slide deposits. This paper describes the geomorphic characteristics of five of the survey areas. Geomorphic mapping shows the presence of slope failures ranging from small (20 km across) mass transport complexes (MTC). The features are associated with debris flow chutes, turbidity flow channels, and debris fields. Analysis of failure planes show prominent grooves or striations related to the mobilisation of slide material down both the continental slope and Exmouth Plateau and into the Kangaroo Syncline. Submarine slope failures can occur at the continental shelf break in about 200–300 m of water and run out to the Exmouth Plateau surface in about 1,100–1,400 m water depths. The largest individual slides in the survey areas have widths of 30 km and minimum run-out lengths of 75 km, though associated turbidity flow deposits likely extend much further. The subsurface expression of the large MTCs illustrates a history of sediment accumulation along the mid-slope followed by repeated slope failure and debris run-out. Sediment accumulation and slope failure processes are actively occurring along the continental slope and submarine landslides thus are a major driver of hazard to subsea infrastructure development. Smaller more frequent slides may pose a greater hazard than large infrequent MTCs.

This study examines channel-scale morphodynamics of ephemeral streams in the onshore Carnarvon basin in arid west-central Western Australia. The rivers in this region have low gradients, the landscape has low relief, and the rates of climatically and tectonically driven geomorphic processes also are low. As a result, the rivers in the Carnarvon alluvial plain are highly sensitive to minor perturbations in base level, channel slope, and fluvial energy. We use channel planform adjustments, stream gradient changes, and floodplain profiles across multiple ephemeral streams within a variety of catchments and flow regimes to determine if tectonically driven land level changes are affecting channel form and fluvial processes. Growth of individual fold segments is shown to have altered stream and floodplain gradients and triggered repeated avulsions at structurally controlled nodes. Aligned perturbations in channel form across multiple channel-fold intersections provide systematic geomorphic evidence for the location and orientation of neotectonic structures in the region. These features occur as a belt of low relief anticlines in the Carnarvon alluvial plain.

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