Anarchaeology.com

[DaveMoore]

The impact of a rock up to five times the size of Chicxulub, that hit near Yucutan, caused a crater found under Antarctic ice as big as Ohio (300 miles across). Purportedly struck 250 MYA. It is thought to be the cause of the Permian-Triassic extinction before to the age of the dinosaurs.

Article
http://news.yahoo.com/s/space/20060602/sc_space/giantcraterfoundtiedtoworstmassextinctionever

Radar image
http://www.space.com/php/multimedia/imagedisplay/img_display.php?pic=060601_crater_radar_02.jpg&cap=Airborne+radar+image+of+land+elevation+in+East+Antarctica.+Higher+elevations+appear+red,+purple,+and+white;+the+location+of+the+Wilkes+Land+crater+is+circled+(above+center).+Image+courtesy+of+Ohio+State+University+.+An+inset+of+the+Chicxulub+crater+is+included+for+comparison.+Credit%3A+Ohio+State+University

Mass Concentration
http://www.space.com/php/multimedia/imagedisplay/img_display.php?pic=060601_crater_gravity_02.jpg&cap=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+

[DavidCampbell]

I believe the concentric uplifts in Pushmataha County, Oklahoma are said to be the result of Australia colliding with North America. It might explain why so many geological oddities in this area are so similar to the ones in Australia, New Zealand and Tasmania.
_________________
David Campbell
"The going's getting weird, so I'm turning pro."