Geopic of the week: Salt casts

Salt Hoppers 045

Salt casts are sedimentary structures that indicate a very saline environment of deposition.  This example was collected from the DeQueen Limestone in Howard County, Arkansas (peppermint for scale). About 146 million years ago, much of Arkansas south of the Ouachita Mountains was under near-shore marine conditions.

The cubes that stand in relief on the underside of this rock bed were once crystals of the mineral Halite – or common table salt.  These crystals grew in the mud of a tidal flat that was periodically flooded with very salty sea water.  The salt crystals were later dissolved, leaving cube-shaped molds that filled with mud, preserving the casts of the Halite crystals.

Ho Ho Ho, Merry Christmas! from the Arkansas Geological Survey

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