A Quaternary Analog for Interpretation of Mississippian Oolites
Published:January 01, 1993
Mark R. Boardman, Cindy Carney, Paul M. Bergstrand, 1993. "A Quaternary Analog for Interpretation of Mississippian Oolites", Mississippian Oolites and Modern Analogs, Brian D. Keith, Charles W. Zuppann
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A Quaternary example of an ooid shoal complex comprised of northern Andros Island (Pleistocene) and Joulters Cays (Holocene) provides insights into ancient ooid shoal deposition and preservation. Criteria that are commonly used in the interpretation of fossil ooid shoals are preserved in the Quaternary example. These include grain composition, lateral variability of shoal subenvironments and adjacent carbonate environments, topography, and to some extent, sedimentary structures. Two subenvironments in particular are easily recognized: (1) the mobile fringe is characterized by high ooid concentrations and well-preserved sedimentary lamination and is topographically elevated, and (2) the stabilized sand flat contains fewer ooids and occurs at a lower elevation. Lagoons, reefs, and offshore skeletal sands are located laterally adjacent to ooid shoals. Muddy tidal flats, however, are not. Evidence of extensive exposure is also well preserved in the Quaternary analog. Sea-level fluctuations as little as 5 m have a profound effect on the site of ooid shoal accumulation and the creation of exposure surfaces.
A comparison of the Quaternary analog to Mississippian oolitic rocks reveals similar grain compositions, sedimentary structures, and to some extent, adjacent carbonate environments. The mobile fringe and stabilized sand flats can also be recognized. In contrast, original topography, exposure surfaces, and eolian features are seldom reported for Mississippian oolitic rocks.
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Mississippian Oolites and Modern Analogs
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.