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PESA WA October Luncheon: New Insights into a major Early-Middle Triassic Rift Episode in the NW Margin of Australia

Thursday, October 18, 2018 @ 12:00 - 14:00

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Guest Speaker: Malcolm MacNeill

Malcolm studied a BSc Geophysics and Planetary Physics at Newcastle-upon-Tyne University in the UK. He spent the formative part of his career within the seismic processing and acquisition discipline working across the globe for numerous service companies and as an independent consultant. He has transitioned into the geological side of the industry over the last ten years. He currently leads of the Regional Australian Exploration team at Woodside Energy based in Perth, Western Australia. His passion is regional tectonostratigraphic and the Palaeozoic in particular.

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New Insights into a major Early-Middle Triassic Rift Episode in the NW Margin of Australia

Malcolm MacNeill

The offshore Roebuck Basin is an amazingly complex and unexpected piece of North West Shelf geology. Large scale seismic geometries within the Triassic section are interpreted to define a complex of lava deltas associated within even a bigger scale rift complex. The location of the magmatic outpouring can be associated with a failed triple junction. Gravity and magnetic modelling supports this model and the apparent thickness of the volcanic complex is up to 10km.

The impact of this rifting is felt regionally along the three arms of the proposed triple junction. The northern arm is easily identified and extends up to the proto-Barcoo and proto-Caswell sub-Basins. The eastern arm propagates with strike-slip motion through the Fitzroy Trough creating numerous transpressional and transextensional features in the Palaeozoic and Early Triassic stratigraphy – previously known as the Fitzroy Movement. The western arm is only recognised to the north of Wombat Plateau. In this area, the Early Triassic thins dramatically and sets up the uplifted outboard edge of a broad epicentre extending across the present-day Northern Carnarvon Basin. The sequences described above across all three arms are overlain by a major unconformity that is interpreted to be a product of these rifting/uplift events.

This talk highlights that a regional approach, incorporating data from multiple sources, geographical areas and formations, assists with the broader understanding of tectonic history of the North West Margin of Australia during the Early Triassic to Middle Triassic.


Thursday, October 18, 2018
12:00 - 14:00


Parmelia HIlton
14 Mill Street, Perth, WA 6000 Australia


PESA Western Australia
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