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Re: extinction events

Large Mesozoic bolides:

mya     diameter(km)    location
65      200+            Chicxulub, Yucatan, Mexico
74       35             Manson, Iowa, USA
117+-8   37             Carswell, Saskatchewan, Canada
183+-5   80             Puchezh, Russia
220     100             Manicouagan, Quebec, Canada
<250     40             Araguainha Dome, Brazil
250     300+            South Gondwana(Rampino hypothesis - NOT confirmed)

Only the really large impacts seem to have left a clear
mark in the fossil record. The Carnian-Norian event seems
to correlate with Manicouagan and the terminal cretaceous
event with Chicxulub. Some have suggested that the P-Tr
event also has an astrogeological component, but no confirmed
crater structure has been documented.