Abstract
Jizan sabkha extends along the southeastern coastal plain of the Red Sea, Saudi Arabia, and is considered as one of the main problems that has a negative impact on infrastructure of buildings. Field examination of the surface of the wet sabkha area indicated the presence of sedimentary surface structures produced by physical forces such as adhesion ripples, tepee polygonal ridges, efflorescent halite pods, and structures produced by microbial activities such as petees and blisters. Microfacies analysis of the siliciclastic and evaporite lithofacies types has been done for sediment samples from the surface, trenches, and cores. The siliciclastic lithofacies type represents the host sediments in Jizan sabkha and consists of sand and mud. The evaporite lithofacies type is distinguished into three microfacies types of gypsum, anhydrite, and halite. The gypsum microfacies types are represented by diagenetic growth of individual lenticular, twinned lenticular, twinned complex lenticular, rosettes, nodular, poikilotopic, porphyroblastic, alabastrine, and clastic gypsum. The anhydrite microfacies types are represented by nodular and enterolithic anhydrite. The halite microfacies types are represented by primary rafts, cumulates, chevrons and cornets, and diagenetic overgrowth and mosaic halite cement. The structural and textural characteristics of the evaporite sediments indicated the formation of primary halite crystals at the brine surface and floor of saline pans, and the diagenetic formation of gypsum and anhydrite below the sediment surface as intrasediment displacive, inclusive, and replacive growth in the wet sandflat and mudflat areas. Recognition of such structural and textural features of the evaporite sediments helps in solving engineering geological problems in Jizan area and allowed also for interpreting the similar sabkha sediments in the rock record.