Composition and stratigraphic distribution of materials in the lower San Andres Salt Unit

The salt bed in depositional cycle 4 of the Permian Lower San Andres Formation, Palo Duro Basin, Deaf Smith County, Texas consists of massive salt interlayered with discrete bands and beds of anhydrite and claystone. The massive salt consists of about 90% halite, with 7% anhydrite and 3% clays disseminated in and among the halite crystals. The halite in this salt bed contains fluid inclusions filled with a (Na, K, Mg)Cl brine, with an average Mg concentration of about 50,000 mg/liter. The anhydrite in the salt will saturate the brines in CaSO4, which in turn may coat the waste package with anhydrite because of the retrograde solubility of CaSO4. This may increase waste package lifetime to failure by corrosion. 16 references, 5 figures, 1 table