[Bass (OP)]

A new gravity study in Antarctica has uncovered evidence of 300-mile wide crater dated approximately 250 million years ago (Permian extinction).  The crater is almost twice the size of the Chicxulub impact crater thought to have caused extinction of the dinosaurs.
http://www.eurekalert.org/pub_releases/2006-06/osu-bbi060106.php

Subduction causes orogeny.

[JimBob]

I still like the Siberian Basalt flows and oxygen shortage and methane abundance that already has data collected to prove it. Guessing the data bnased on a process not really well understood, no matter how well the theoreticl model works is still not as accurate as finding the "last fusulinid" or the first Hindeodus parvus (a type of conodont, for those who do not speak geologist.) A K-Ar date would also work.

There is nothing like a rock for geologic data.

Still, nice to know but for me meteorites are not a really good answer. All biologic systems would logically be effected the same way.





The mind is like a parachute. It works best when open.  -- A. Einstein