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Title
Sheep Rock Unit, John Day Fossil Beds National Monument #68868111
Description
The John Day Basin is a fossil record that spans over 40 million years. The predominant exposures of green rock seen on Sheep Rock are a multitude of reworked layers of volcanic ash. The rich green color of the claystone was caused by chemical weathering of a mineral called celadonite. This happened millions of years ago as water moved through the alkaline ash beds under high pressure.