Diabase Sill intruding Crystal Spring Formation.

The green-colored rock in this photo is a 1 billion year old intrusion called diabase (chemically similar to basalt). Because it intrudes parallel to the layering in the country rock, it is called a sill. The country rock is the Proterozoic Crystal Spring Formation. Throughout the Death Valley region, talc deposits formed at the contact of the diabase sills and dolomite of the Crystal Spring Formation. The light-greenish rock on the far left of the photo is Precambrian basement gneiss.

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