Lithofacies and biofacies of the Middle and Upper Devonian Sultan Formation at Mountain Springs, Clark County, Nevada: implications for stromatoporoid paleoecology

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Abstract
The Sultan Formation is a Middle and Upper Devonian inner shelf carbonate sequence in southern Nevada containing four stromatoporoid-dominated biofacies. Reported herein is a study of the Ironside Dolomite and Valentine Limestone Members exposed at Mountain Springs, Nevada. Eight lithofacies are distinguished and interpreted as a transgressive sequence, with deposition ranging from the supratidal zone to just below wave base. Each of the biofacies is unique and confined to a specific depositional environment as interpreted from the lithofacies reconstructions. The purpose of the study was to gain a better understanding of the range of ecologic conditions—physical, chemical, and biological—to which these stromatoporoids were adapted.Based on the research, it is concluded that stromatoporoids flourished in a variety of nonreef habitats which ranged from highly stressful peritidal environments where only stromatoporoids were accommodated to less stressful offshore habitats where other organisms may have been in direct competition. Although habitat generalists are usually poor competitors, these stromatoporoids appear to have been an exception. Their ability to colonize a variety of substrata, their broad tolerances to chemical conditions and circulation patterns, and their emphasis on high rates of lateral growth have permitted them to simultaneously occupy unstable tidal channel embayments and more benign offshore habitats.