How to reconstruct the Southwest Pacific, when subduction has erased its own tracks


Models for reconstructing the past positions of tectonic plates have become extraordinarily powerful, but will always be limited by available data. The principal constraint on plate reconstruction is provided by marine magnetic anomalies - "seafloor stripes". For most of the oceans, this works well - but in the southwest Pacific, late Miocene reversal of the direction of subduction in the Melanesian volcanic island arcs has resulted in the destruction of the back-arc basins that recorded their earlier migration away from Australia. Current models for plate motion in this region have been built on some widely accepted assumptions about the history of arc motion and arc-plateau collisions - but there is evidence that these assumptions are wrong. What can we do to sort this out? The answer has implications for the history of motion of the Australian plate, and for the prototypical example of arc-plateau collision.


Bob Musgrave is a geophysicist specialising in palaeomagnetism and tectonics. After a PhD at the University of Sydney working on the tectonic history of the Solomon Islands, Bob's peripatetic career took him to post docs at Victoria University of Wellington, New Zealand, the ANU, and the University of Tasmania, before heading to the US to work for the Ocean Drilling Program. Returning to Australia, Bib was a Senior Lecturer at La Trobe University, before closure of the Geology Department there - the first of many - saw him join the Geological Survey of NSW, based in Maitland in the Hunter Valley. Although redundancy from GSNSW in 2021 saw Bob "officially" retired, he continues to operate his palaeomagnetic lab - the PALM lab - at the University of Newcastle.

Questions? Please get in touch with Gideon or Renjie.



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