Chemical characteristics of the brines and sediments of the Ayun Musa and El-Shatt sabkha sites indicate an increase in the salinity gradient of the groundwater, passing upwards through the sabkha sediments. The potassium content of the pore water through the vertical profile of the sabkha at Ayun Musa, calculated versus ionic content of two gypsum crusts within the sediment and from the overlying surficial halite demonstrates that there is a clearly defined rise in pore-water concentration through the sabkha profile, from the ground-water table up to the surface. Evaporative pumping is probably the active process responsible for the upward capillary movement through the studied sediments.The calcium sulfate present in the sediment of both sabkhas is in the form of gypsum and is believed to be the primary sulfate product. It is present as crusts of gypsum rosettes and as fine disseminated lenticular crystals within a elastic matrix. The depositional profile at both sabkha sites is usually topped by halite, but the halite at Ayun Musa is a surficial crust (from capillary growth) while the deposition at EI-Shatt is both in the form of subaqueously-grown layers as well as surficial crusts. The profile at El-Shatt suggests that the thick halite deposits in the low areas of the sabkha form by the solutional reworking of marginal salt as well as directly from brine concentration after flooding. Because the sediments of both sabkhas shows any significant diagenetic alteration, these two sites appear to have been affected only by the very earliest stages of diagenesis.The Ayun Musa sabkha is a typical continental type receiving waters from rainfall that dissolve salts from the surrounding Miocene sediments and concentrates them within the capillary zone of the soil profile by evaporative pumping, while the EI-Shatt sabkha is largely marine, and receives its water through direct input of seawater from the Gulf of Suez by both flooding and by seepage recharge.