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Liesegang banding in jointed, deformation-banded sandstone, Sheets Gulch, Circle Cliffs uplift, Utah.

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Age & Formation: 
Navajo Sandstone of Jurassic age, ~170 Ma, laced with deformation bands that formed in latest Cretaceous to Eocene, i.e., ~70-55Ma.
In Sheets Gulch, which is a vast upland landscape of perfectly exposed Navajo Sandstone, blocks and pieces of very resistant deformation banded sandstone lie all over the ground in places. In contrast to the normal sandstone bedrock, these blocks and pieces have been made more resistant because of cataclastic deformation and cementing along deformation bands and/or precipitation by ground water of secondary minerals such as hematite, limonite, and manganese. These secondary minerals dominate the appearance of this specimen. The blocky nature of this piece is controlled by preferred orientations of deformation bands. The impermeable bands compartmentalized the flow of ground water in structures-bounded ‘pipes.’ Heavy concentrations of secondary minerals occur along the walls and at intersections of structures. Because the host sandstone (which is still preserved in the center of this specimen) is homogeneous and quite porous, solutions moving through lend themselves to the more cyclic diffusive precipitation in the form of classic Liesegang banding.
I collected this, as already emphasized, in Sheets Gulch, back in the late 1990’s. It is a bizarre piece, which I really like. Most people who see this might not even think of it as a rock, more likely some old part from a wrecked car, …a part collected in a junk yard.