Should this Antarctica impactor be concurrent with the Siberian Traps volcanism then the impactor could have been the cause. Just as the K-T impactor is concurrent with the Deccan Traps volcanism.
Large as it is I think that this crater might not have been the only cause of the Permian extinction. I am inclined to think there may be a very major crater buried under the Siberian lava flows. I base this conjecture on the following:
Recent studies by Chattergee (sp?) in India point to the existence of the Shiva Crater and the edge of the Deccan Traps, about 200 by 400 miles and the same age (65 my) as the Yucatan (dinosaur) crater. This would be the same general mass as the propoposed Antarctic impactor and only killed 70% of life forms.
The Chesapeake Meteor (35 mya) was 50 miles in diameter, and the Popigai (Siberia) crater 60 miles wide, and the Toms River crater, 9 miles wide, all falling about the same time killed less than 50% of life.
As we saw during the recent Jupiter bombardment, boloids come in families.