Major U.S. Salt Deposits

Figure 1 shows the location of major bedded salt deposits and salt dome basins in the U.S.

Figure 1

Salt Domes

• Large, nearly homogeneous formations of salt (sodium chloride)
• formed about 30 million years ago
• formed when less dense salt flowed upward into overlying formations
• formed long, finger-like projections (see Figure 2 below)


• Depth to the salt can be hundreds to thousands of feet



• Top width ranges from 0.5 to 2.5 miles



• May have a caprock on its upper surface (see Figure 3 below)



• Extensively explored for minerals and mined for more than 10 years

Figure 2: Salt Dome Piercement

Figure 3: Caprock

Bedded Salt

• Formations of salt (sodium chloride) found in layers interspersed with materials such as anhydrite, shale, dolomite, and other more permeable salts (e.g., potassium chloride)



• Formations are tabular (see Figure 4 below) and can contain significant quantities of impurities



• Often found at 500 to 2,000 feet below the ground surface



• Have thickness of 1,000 to 3,000 feet

Figure 4: Midland Basin Stratigraphy Showing Bedded Salt. Source: University of Texas - Bureau of Economic Geology

Other Geologic Features of Salt Formations

• Generally found at depths below the water table (top of the groundwater surface)



• Low overall permeability (groundwater movement is slow)



• Adjacent groundwater is usually of poor quality



• High salt content



• High mineral concentrations



• High total dissolved solids