Primary Features in A Potash Evaporite Deposit, The Permian Salado Formation of West Texas and New Mexico
Tim Lowenstein, 1982. "Primary Features in A Potash Evaporite Deposit, The Permian Salado Formation of West Texas and New Mexico", Depositional and Diagenetic Spectra of Evaporites - A Core Workshop, C. Robertson Handford, Robert G. Loucks, Graham R. Davies
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The late Permian Salado Formation is up to 700 m in thickness in New Mexico and Texas, and it contains a complex array of both primary (including syndepositional diagenetic) and secondary minerals, textures, and fabrics. Primary textures and fabrics have been identified for saline minerals such as gypsum (now pseudomorphed by anhydrite, poly-halite, halite, and sylvite as vertically oriented prisms, wave-rippled grains, mud-incorporative euhedra, and laminae made of small crystals) and halite (vertically oriented “chevrons” and “cornets,” equant hoppers, laterally linked “hopper rafts,” “cumulate” aggregates, and mud-incorporative cubes).
Vertical sequences are organized into cycles consisting of either 1) mud-free halite grading upward into muddy halite (30 cm to 6 m in thickness), or 2) mud, followed by laminated anhydrite-magnesite, grading into laminated anhydrite with primary gypsum textures and fabrics, followed by mud-free halite (with primary “cumulate” and syn-taxial bottom growth features), and ending with a muddy halite cap (1 to 11 m in thickness). Within a cycle, the primary chemical environment has evolved from relatively dilute waters initially producing alkaline earth carbonate to brines ultimately halite saturation. By comparison with modern evaporite environments, the primary sedimentary environment in a vertical sequence is a “shallowing upward” cycle beginning with a shallow perennial lagoon or lake at alkaline earth carbonate saturation, progressing to one saturated first with gypsum and then with halite, and ending finally as a dry salt pan and saline mudflat at halite saturation.
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Geologists do not often have an opportunity to examine evaporites, whether in outcrops as badly weathered exposures, or in the subsurface, where evaporites are not as frequently cored as other rock types. Nevertheless, evaporites are important economically (mineral resource, seals for hydrocarbons, disposal sites for radioactive wastes, etc.) and geologists are, by necessity, becoming more aware of their origins. This workshop is intended to increase awareness and provide useful information for comparison to other evaporites, all of which should eventually benefit geologists in their efforts to understand the depositional and diagenetic spectra of evaporites.