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28 July 2011
A faulted chert nodule
Here is a trio of concentrically-zoned chert nodules in Mississippian Castle Reef Dolostone, exposed at Sun River Canyon, Montana, just downstream from the roadside outcrop of the French Thrust: If you look closely at the lowermost of the three chert nodules, you’ll see it’s been split and offset by a small fault. Here are close-up portraits of all three, concluding with the most interesting one (the deformed one): Hope all …