Thanks for posting this, Chris. I am wondering about the nanodiamonds. I don't recall that these are usually markers of a major impact, but I'm woefully out of date on things!

My recollection is that certain minerals (iridium, etc.) and shocked glass would be more indicative of an impact. However, if the impact brought kimberlite-type rock to the surface and somehow blew it apart, I would imagine that nano-diamonds might be found.

Anyway, won't go looking for one to put in a ring soon! (hehehe)

Enjoy!