Modern dynamics, morphology and habitats of slope-confined canyons on the northwest Australian margin

Repeat multibeam mapping of two slope-confined canyons on the northwest Australian margin provides new understanding of the processes that are active in shaping these environments. The Cape Range and Cloates Canyons initiate on the mid- to lower continental slope, but are connected to the shelf via small channels and gullies. These canyons were first mapped systematically with multibeam sonar in 2008 and were remapped in 2020 during a biodiversity survey that also collected high-resolution imagery and biological samples from a deep-water Remotely Operated Vehicle. Comparison of features between the two surveys indicates active sliding, minor headwall retreat and continued excavation of deep floor depressions, reflecting the action of high energy turbidity currents. Significantly, intact blades of displaced seagrass imaged throughout both canyons at depths up to 4200 m indicates that sediment sourced from the adjacent continental shelf is being channelled through these canyon systems. Sedimentation likely regulates benthic communities in these canyons, with imagery showing highest densities of sessile invertebrates in habitats protected from sedimentation (e.g. rock overhangs). Repeat mapping provides an understanding of the dynamics of these canyons and a context for assessing and monitoring the stability of the seabed habitats within a marine reserve. Citation: Alexandra L. Post, Rachel Przeslawski, Rachel Nanson, Justy Siwabessy, Deborah Smith, Lisa A. Kirkendale, Nerida G. Wilson, Modern dynamics, morphology and habitats of slope-confined canyons on the northwest Australian margin, Marine Geology, 2022, 106694, ISSN 0025-3227, https://doi.org/10.1016/j.margeo.2021.106694.