ABSTRACT

Sabkhas are common evaporite-rich sedimentary environments that in many cases are associated with dolomites that contain hydrocarbons. The Gulf Coast Jurassic and Cretaceous include several subsurface examples (e.g., Smackover, Buckner, probably Norphlet Formations) as do older formations in the upper Paleozoic of Texas and neighboring states.

This study concentrates on Recent sabkha sediments around the margins of the Gulf of California (Sonora State), together with Cretaceous outcrops in southern Arkansas and central Texas, and Permian strata in southeastern Utah and New Mexico.

Sabkhas in the Recent of Mexico are dominated by trona and other sodium carbonate minerals that have been precipitated from continental groundwater derived from volcanics in the interior of the Gran Desierto. A hydrologic system similar to that recognized in Abu Dhabi sabkhas is confirmed, since most of the Sonoran evaporites are derived by evaporative pumping of continental groundwaters. Near the coast, groundwater chemistry becomes marine in character, although of exceptionally high salinity.

The Cedar Mesa Formation (Permian) of Utah is primarily composed of eolian dune sandstones. To the southeast, these sandstones include gypsum eolianites, deflated from neighboring sabkhas. Interdune deposits in this area include thin limestones, some of which contain marine fossils. The sabkha sediments display many of the textures and structures described from Abu Dhabi, including enterolithic anhydrite and "desert rose" gypsum crystal clusters. Sabkha features in the Guadalupian of the Seven Rivers area of southeastern New Mexico are also described.

The Cretaceous (De Queen Formation) sabkhas of Arkansas illustrate very well the dual source of sediment in this environment. Siliciclastic mud (containing charophytes) was washed in from the landward side during floods, and ooliths were contributed from the seaward side during storms. Changing patterns of salinity are documented by foraminiferal and ostracod abundances and diversity in fine-grained sediments. Sedimentary structures include desert roses and lenticular (discoidal) gypsum and related anhydrite nodules, and palmate gypsum in supratidal ponds.

This variety of examples provides additional templates for recognizing and understanding subsurface sabkhas and associated dolomite reservoirs.