I guess I missed the article from 2008 that described the evidence for a post-Paleoprotozoic (1.2 bya - 330 mya) impact crater in the area of Santa Fe, New Mexico. A story this month in Astrobiology magazine says the original crater was probably 6-13 km in diameter, or about 5 to 10 times the size of Arizona's Meteor Crater at 1.6 km.
The University of New Mexico is organizing a public field trip for summer 2011 to examine the exposures that document the impact structure. [right, shatter cone outcrop. Credit UNM]
Ref: S. Fackelman, et. al, (2008) “Shatter cone and microscopic shock-alteration evidence for a post-Paleoproterozoic terrestrial impact structure near Santa Fe, New Mexico, USA,” Earth and Planetary Science Letters 270, 290-299.