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
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 2: Salt Dome Piercement
Figure 3: Caprock
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
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