 Click on the image for a closer view.
If you take BB gun, and shoot it into a wet mud-pie at a low angle of about 30 degrees you will see that these oval impact structures are consistent with low angle impacts in to a semi fluid surface.
To complete the image, and get the under lying ripples, blow a wind across your mud-pie with enough force to whip the surface into the driven chevron shaped waves we see here while simultaneously hitting it with many BBs coming from the same direction as the wind.
If you want to finish the image completely your huricane force wind should be hot enough to partially lithify the surface.
The patterns of movement in the fluidized, impacted, and partially lithified surface are consistent with a total time of material movement of only a couple of short seconds. This is only part of it. The whole valley was hit.
I have many question for this place.
What was going on upwind at the source of the impactites and blast wind? What do we expect the ground should look like there?
This event is, geologically, a very recent event. If you look closely at the top left of the image you can see where one of the ejecta splashes is over-lapping one of the ancient meanders of the river. And that the river hesn't changed its course and modified the ejecta splash since that time..
Glacial lake Missoula, and its ice damn on the Clark Fork River in northern Idaho are down range. The event that produced these pristine oval impact structures may have been the trigger that broke up the ice damn on the Clark Fork River.
I have Many, many questions for this place that, if answered, would only bring more questions.
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