• Specimen Number

  16

• Description

  Block of rock with interbeds of limestone, with gray-blue alternating with brown-stained.  Fizzes with dilute acid.   Closeup shows granular texture with some finer-scale bedding and crystal regrowth in prisms normal to bedding planes. This is neither a limestone mud nor grainstone.

• Classification

  Sedimentary. Limestone. Crystalline.  Bedded.

• Location & Occurrence

  For limestones in the state, the U.S. Geological Survey lists  only "Upper Cretaceous fossiliferous limestone and marl" and "Wilcox Group.....some limestone and glauconite." Neither looks like our specimen.  "Limestone occurs as part of the caprock at this dome, and as Cretaceous limestone brought to the surface by two salt domes in Bienville Parish." Quotes are from a Lousiana State Survey report compiled by Peggy B. Perazzo (see link below).

• Geological Age

  Late Cretaceous.

• Geoheritage

  Salt domes are fascinating and important features responsible for trapping much of the petroleum and gas for which Louisiana is well known.  Yet the general public is virtually unaware of them. They rise slowly because salt is less dense than adjacent rocks, so it squeezes upward.

• Links

  Link to State Geological Map from USGS.  Link to Louisiana Geological Survey. Stone Quarries and Beyond.

• Other

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