Benthic Assemblages as Indicators of Sediment Stability: Evidence from Grainstones of the Harrodsburg and Salem Limestones (Mississippian, Indiana)
Howard R. Feldman, Mark A. Brown, Allen W. Archer, 1993. "Benthic Assemblages as Indicators of Sediment Stability: Evidence from Grainstones of the Harrodsburg and Salem Limestones (Mississippian, Indiana)", Mississippian Oolites and Modern Analogs, Brian D. Keith, Charles W. Zuppann
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Within the Mississippian (Valmeyeran) strata of Indiana, the uppermost Harrodsburg and lowermost Salem limestones contain a variety of grain- stone facies that were deposited within a tide- and wave-dominated, shal- lowing-upward sequence. Compositions of autochthonous fossil assemblages in each facies are interpreted to have been constrained primarily by sediment stability. For example, echinoderm-bryozoan-brachiopod assemblages apparently thrived on stable substrates. Conversely, gastropod-domi- nated assemblages lived on frequently reworked, tidally influenced substrates. Low-diversity assemblages lived on substrates that were almost continually reworked. Faunal diversity decreased with increasing sediment mobility because of the increased (biological) energy required to maintain a life position at the sediment-water interface. Within modern analogs, a decrease in faunal diversity commonly correlates with increased sediment mobility.
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A coincidence of tectonic, eustatic, and geochemical conditions resulted in substantial deposits of oolitic limestone during later Mississippian time in the continental United States. These oolitic limestones have formed petroleum reservoirs with favorable primary and secondary recovery characteristics. Significant potential reserves in stratigraphic traps remain to be discovered and developed in these reservoirs.