Abstract

Salt Flat sabkha is a dried playa lake located in the Salt Basin, a north-south trending intermontane basin about 145 kilometers east of El Paso, Texas. Salt Flat is a ground-water fed continental sabkha dominated by fluvial-lacustrine processes. This study of Salt Flat sabkha emphasized the surface features in and around the playa, the recognition and interpretation of the sedimentary structures and textures in the shallow subsurface sediments. At present the sabkha flat of the Salt Flat sabkha is comprised of a lacustrine unit and an evaporite-carbonate unit. Concomitant with sabkha flat aggradation, bajada and sand flat progradation continues. Thus, a continental sabkha sequence is characterized by a basal lacustrine unit of fine grained, horizontally laminated sediments with occasional interbedded carbonates and coarse basal lag. The lacustrine unit may be followed by an evaporite unit consisting of a millimeter-laminated, varve-like sequence of gypsum and micrite (which may be dolomitized). Diagenetic imprints in this unit are evidenced by displacive nodular and enterolithic gypsum or anhydrite. The algal-laminated portion of the sequence shows stromatolitic structure. Rip-up clasts, which are often found in the sabkha flat, are preserved as intraclast breccia. Overthrust ridges, when preserved, occur as tepee-like structures. These tepee-like structures, along with biscuit-shaped algal structures, indicate subaerial exposure and zones of preferential ground water resurgence. Vertically aligned selenite crystals may indicate desiccation areas of the sabkha flat edges.