Petrologic Method for Distinguishing Eolian and Marine Grainstones, Ste. Genevieve Limestone (Mississippian) of Indiana

Abstract

Published descriptions of carbonate eolianites of pre-Pleistocene age are rare. Eolianite grainstones of the Ste. Genevieve Limestone (Mississippian) near Corydon, Indiana, contain a diverse assemblage of grains, including various skeletal grains, ooids (some broken and abraded), peloids, well-cemented intraclasts, and abundant quartz silt. Sphericity of originally tabular carbonate grains is generally high. Eolian grainstones are laminated, and in places grain size coarsens upward within laminae. Vadose cement is rare, and solution packing is extensive. Marine grainstones, which probably formed on shallow shoals or an open platform, are also common in the Ste. Genevieve section and contain a diverse assemblage of skeletal grain types, ooids, peloids, and intraclasts; however, a single grain type (such as ooids) commonly dominates each individual unit. Detrital quartz grains are rare. Sphericity of skeletal grains not originally spherical is low. Fine laminations are not present, and no systematic grading is found on a thin-section scale. Fossils larger than 4 mm occur in the marine units. Solution packing is minor, and some marine cement is present. Petrographic and stratigraphic data suggest that the eolianites formed due to lowering of sea level and not due to buildup of islands above sea level. End_Page 49-------------------------