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PESA WA : Evening talk – The last day of the Permian – or just another day in WA? – A Discussion
Thursday, 1 October, 2020 @ 6:00 pm - 8:15 pm (Australia/Perth time)Free – $30
The last day of the Permian – or just another day in WA? – A Discussion
Prof. Chris Elders
Thusday 1st October 6pm (for talk start at 6.45pm)
PESA Members: $15.00 (Members must Log on to the PESA website to see the member prices)
PESA Students Members: Free (registration is essential)
Bookings close Thusday 4pm for venue and catering purposes.
We have recently been presented with the intriguing suggestion that the Bedout High, and other circular structures in the Roebuck Basin, might once again be interpreted as the result of meteorite impacts. Given that these structures formed at, or near to, the end of the Permian such impacts might provide a plausible mechanism for the mass extinction that occurred at this time and the associated deposition of organic rich source rocks that followed early in the Triassic.
An alternative plausible explanation for the Bedout High is that it is igneous in origin. Comparison with analogues is therefore desirable to try and distinguish between these alternative interpretations. The recent drilling of the peak ring of the Chicxulub impact crater by the International Ocean Discovery Program (IODP)/International Continental Scientific Drilling Program (ICDP) provides an unprecedented insight into the events that occurred in the minutes, hours and days after the meteorite impact – dubbed “the first day of the Cenozoic”. Numerical modelling also describes the process by which impact craters and peak rings are formed, providing some testable criteria against which interpretations of impact structures can be compared. Chief among these is that uplift is only a transient feature, and the peak ring is associated with subsequent collapse. Given that the initial impact of the Chicxulub meteorite likely resulted in fluidisation and vaporisation of crustal rocks to a depth of c. 20 km, it is highly unlikely that that the layered geometries observed around parts of the Bedout structure would survive intact.
Eruption of magmas in the Siberia traps are suggested as one of the causative mechanisms for the end Permian mass extinction. The eruption of the Siberian traps was perhaps more prolonged than a short lived event triggered by a meteorite impact. The extend and severity of the anoxia that resulted is also the subject of ongoing debate with recent work in the Perth Basin suggesting a variety of environmental conditions at this time.
This will be a short presentation, with plenty time for discussion. Please bring your own observations, thoughts and ideas to share.