http://www.space.com/php/multimedia/imagedisplay/img_display.php?pic=060601_crater_gravity_02.jpg∩=Gravity+fluctuations+beneath+East+Antarctica+measured+by+GRACE+satellite.+Denser+regions+appear+more+red;+the+location+of+the+Wilkes+Land+crater+is+circled+(above+center).+Credit%3A+Ohio+State+University+
Bedout High: c.250 MYA, ~200km diameter The Bedout structure 300km west of Broome, in the Canning Basin off the coast of Western Australia, has been sited as one of the possible impacts that contributed to one of the greatest extinction events known. At the end of the Permian Period, around 250 MYA, it has been estimated that more than 90% of marine species, and 70% of terrestrial species, may have become extinct. The extinction event seems to have been a sudden, global occurrance, lasting less than a million years (which in geological terms is very rapid).
http://home.alphalink.com.au/~dannj/craters.htm
So many craters, so many extinctions...
I 'discovered' another one recently, named in 2003 IIRC. Not yet on the map of Australian Impact Craters.
Google pic follows...