Salt diffusion in interstitial waters and halite removal from sediments: Examples from the Red Sea and Illinois basins

Abstract

Large thicknesses of bedded halite can be removed in subsiding sedimentary basins by vertical diffusion of dissolved salt in interstitial waters over geologic time scales. Calculations show that at least 10 m to 40 m of halite may have dissolved and diffused through the Red Sea sediments overlying the salt beds, since cessation of salt deposition approximately 5.3 million years ago. The total amount of salt diffused out of the sediment column over geologic time is five to twenty times the amount of salt that currently exists in the porewater column. If upward flow in the past occurred at even small rates, 10 −3 m/yr, the amount of halite removed could have been ten times as great, 500 m. Unlike the Red Sea Basin, no halite beds are known in the Illinois Basin in spite of the fact that interstitial waters with as much as 200%. TDS (approximately 220 g/L) occur. Calculations show that if a halite bed had been deposited at the base of the Illinois Basin in Cambrian time, it would have been completely removed from the stratigraphic record had it initially been less than 60 m to 130 m in thickness. A significant thickness of halite deposited in sedimentary basins may thus be removed during active burial of salt beds, and before exhumation and exposure of the salt beds to shallow meteoric waters.