Geophysical investigation of the evolution of William’s Ridge and Broken Ridge, Kerguelen Plateau

Magri Luca1, Whittaker Joanne M.1, Coffin Millard F.1, Gürer Derya 1,2

1Institute for Marine and Antarctic Studies, University of Tasmania, TAS 7004, Australia; 2School of Earth and Environmental Sciences, The University of Queensland, QLD 4072, Australia

The Kerguelen Plateau is the second largest submarine plateau on Earth and is composed of both oceanic and continental crust. Its presumably dominant oceanic crust is commonly attributed to the Kerguelen mantle plume, probably interacting with mid-ocean ridges, and ranges in age from ~120 Ma in the south to ~35 Ma in the north. In situ continental rocks recovered to date from the Kerguelen Plateau (Elan Bank) are Proterozoic in age and bear affinities with similar rocks in once-nearby East Antarctica, eastern India, and Western Australia. Extending for ~300 km southeast from the ~100 Ma Central Kerguelen Plateau is William’s Ridge, which separated at ~43 Ma from its conjugate ~95 Ma Broken Ridge by seafloor spreading along the nascent Southeast Indian Ridge.

In early 2020, a 57-day voyage was undertaken in the Southern Indian Ocean, aboard Australia’s Marine National Facility, the RV Investigator to expand our knowledge of lithospheric rifting, breakup, and initial separation processes between William’s Ridge and Broken Ridge. Multichannel seismic reflection (MCS), sub-bottom profiling, multibeam bathymetry/backscatter, and gravity data were acquired, along with dredged rock samples.

We present initial results from the post-expedition analysis of MCS acquired from the conjugate features. Using these profiles, we aim to better understand their formation and evolution during breakup of the once-contiguous Kerguelen Plateau and Broken Ridge. Using the newly acquired MCS data, we investigate the depositional and tectonic history of the two conjugate divergent margins. By defining the main stratigraphic and structural characteristics of the margins, we reveal the relationships that exist between the pre-rift, syn-rift, and post-rift sequences, determine the margin structural domains, and the dominant deformation processes related to each domain.


I studied Geology for my BSc in University of Pavia (Italy). I did my MSc in University of Bologna (Italy) about Geology and Field. During my master I did an internship in Cadiz (Spain) at University of Cadiz.

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