An Ordovician section similar to that near Eureka is well displayed north of Las Vegas Valley as far east as the Dry Lake Range. About 10 miles farther east, in the Muddy Mountains thrust plate, a section of impure carbonate rocks has been regarded as probably of Ordovician age. An assemblage of conodonts indicates an Early Ordovician date for that unit, here described as the Monocline Valley Formation. No Ordovician rocks are known east of Virgin Valley.

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