Massive New Crater Field Discovery In Wyoming

[jasong]

https://trib.com/news/local/casper/a-wyoming-crater-field-may-offer-insights-into-our-solar-systems-workings/article_0e0eae2c-4426-11ed-bcf6-e7dbc7b57469.html

There are varying theories as to the origin - including that we once had a second moon! Or maybe smaller orbiting sub-moon type body which got shattered by an impact and rained onto Earth.

The article doesn't cover this, but of note is that the formation in which this massive field of fossil craters is found in matches up with the largest extinction event in history - the Permian-Triassic extinction event - which is much larger than the one that killed the dinosaurs 200 million years later.

In any event, this is an extremely interesting discovery. I believe this field probably extends beyond just Wyoming and may be a national scale, or maybe even potentially a global scale occurence with more research. The craters themselves are visible on aerials if you look closely, but are so old that any actual meteorite material has long since weathered away, but shock glass is still there.

 

[Jim in Idaho]

Absolutely incredible! Thanks for posting!

Jim

[GB_Amateur]

280 million years old and not discovered until the 1990's; disagreement between researchers regarding its origin; real scientific research in action!  Good stuff.

[Steve Herschbach]

I think impact geology presents a whole new way of looking at classic geology, and may end up explaining many structures that right now have people scratching heads. The only real difference between the surface of the moon and the earth is erosion. We have been hit just as much, if not more, by large objects. Many shattered huge areas, creating the structures that later allowed for ore deposition. Very new, very kind altering stuff. Never a peep about in in any geology books until very recently.

http://www.impact-structures.com/wp-content/uploads/2017/09/Impact-Final-2.pdf

[jasong]

Interesting pdf, will take some time to read through that one. Big difference between surface of moon and Earth is active tectonics too, that's what brought this old fossil impact field back up to the surface as the Rockies rose up.

There is actually another huge impact structure here in Wyoming that was discovered by O&G drilling and/or thumper trucks (geophysical), but it's not exposed on the surface at all, it's buried 4000 feet deep. The structure itself can still be discerned underground though. It's about 200 million years old, and it just goes to show that some of these older fomations are probably covered with paleo-impact structures all over the entire planet.

They tend to form anticlines. Which means buried impact structures could be economic oil and gas traps - in fact this one has wells on it. But some Carlin-type gold mineralization also likes anticlinal type structures as well, so there is a potential that buried impact structures in Nevada could contained enriched Carlin-type mineralization. It would be an interesting method of theoretical gold exploration that I bet few to zero people are doing right now.

Notably, the KT Boundary also contains a number of of precious metals from the fallout dust from the meteorite that killed the dinos. Iridium is used as a marker element, for one. 

 

[Jim in Idaho]

There's a huge one a bit north of me. The highest peaks in Idaho are on the rim of it. It's estimated to be 1,000 -500 ma. The Beaverhead crater. It was discovered late, too.

Abstract
The Beaverhead impact structure in southwestern Montana and eastern Idaho is an allochthonous^*  fragment of a large impact structure (~100-km diameter) that was transported some distance eastward during the Cretaceous Sevier orogeny. It is the first tectonic fragment of a large impact structure identified in the geologic record. The present evidence for impact consists of shatter cones, pseudotachylites and planar deformation features in quartz. The age of the impact is not well contrained but is estimated to be Neoproterozoic to Cambrian (1,000-500Ma).

^* allochthonous – found in a place other than where they and their constituents were formed

[Steve Herschbach]

I guess I would have been better saying “geologically active.” The point was we have been every bit as plastered with massive hits as that ball in the sky, and texts on classic geology only talk about plate tectonics and mountain building as causes of land deformation. The older a geologic layer is, the more likely it is that it  will have been impacted in some way. It’s a whole new way of looking at why structures are the way they are, more a mix of plate tectonics, but with massive impacts breaking things up. A large deep impact will also inject a great deal of heat, and may have triggered volcanic events in some regions. Lots to think about. Why did Gondwanaland seemingly just decide to break up and drift around one day? Asteroid strike?

[Hardtimehermit]

Heat would be my guess, all the heat from the core. 😉

[GB_Amateur]

13 hours ago, jasong said:

There is actually another huge impact structure here in Wyoming that was discovered by O&G drilling and/or thumper trucks (geophysical), but it's not exposed on the surface at all, it's buried 4000 feet deep. The structure itself can still be discerned underground though. It's about 200 million years old, and it just goes to show that some of these older fomations are probably covered with paleo-impact structures all over the entire planet.

That description fits the Kentland Crater in NW Indiana.  My parents used to own land over it so I know a bit about it (including some unpublished tidbits.  😁)  It was discovered by accident only many decades after it was producing limestone (for roads).  In the 1960's when a geologist hypothesized the limestone dome was caused by a meteoroid, the quarry owners tried to nix that idea since (apparently) they thought their operation would be shut down -- kinda like what happens when Native American burial sites are discovered.  In the late 1970's some geologists from University of Kansas showed up to research its age.  My dad contacted them and one even came to dinner at our house.  I was able to pick his brain a bit.  Their conclusion which was published in 1978 was 250 million years with an uncertainty of (plus or minus) 100 million years, if I remember correctly.  The Wikipedia article shows that now there are two competing ages (97 million and 300 million -- but Wikepedia not quoting uncertainties 😠).

BTW, on a side note (but definitely relevant to detectorists) is that one of the geologists spent his free time in the area roaming through the countryside looking at rock piles made by farmers clearing their fields of plow damaging material.  (Those are/were fairly common.)  Apparently he had found a few meteorites in those over the years.

[Bear]

Impact structures are discussed a lot in geology courses.  

To lengthy to discuss here but the driving forces behind tectonics, including the formation and break up of supercontinents is likely a combination different processes.