Glacial "dropstone" in laminated siltstone of Proterozoic Kingston Peak Formation.
Much of the Kingston Peak Formation consists of "diamictite", a poorly sorted mix of boulders, cobbles, pebbles, sand, and silt, a deposit with many similarities to glacial till. In this photo, larger cobbles, called "lonestones", are surrounded by fine-grained, laminated material that indicates low-energy depositional environments. Note that the laminations deflect around the cobbles on both sides. It seems that the cobbles just "dropped in" on the finer material --and the going interpretation is that they were ice-rafted cobbles that floated out over the silt, and dropped down on the silt as the ice melted.

This particular rock is from just southeast of Death Valley National Park. Click here to see the Geology of Death Valley National Park through photos.

And here's another image from the same general area --more diamictite in the Kingston Peak Formation.

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