Page 435 - Carbonate Facies in Geologic History

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Plate VII. Coated Rounded Bioclastic Grainstones,
Standard Microfacies 11

(A) Rounded clam shells and gastropod tests mixed with smaller ooids and black
peloids, coarse grainstone. Some larger particles have micrite rinds caused by
boring filamentous blue-green algae and indicating particle movement in shallow
sunlit water less than 10m deep. Particles are completely and evenly lined with
fibrous druse but much original pore space is unfilled (white). Large blocky
crystals on lower left are replacement selenite. Sample DK-51 (37) from shoal in
Late Jurassic (Arab D Formation) on the Arabian Shield. Facies J 10, Chapter IX.
Peel, x 18

(B) Shoal grainstone-packstone, coated and rounded. Sample MS-13-A is
from the Mississippian Salem limestone, Cleveland quarry, Harrodsville, Indiana.
Particle types are worn bioclasts of bivalves, brachiopods, gastropods, and en-
dothyrids. Many particles have dark micrite rinds (see above). There is no drusy
lining (marine cement?). The original void space was pardy fIlled by peloidal
calcisilt and remaining portion with coarse crystalline calcite; upper side of the
sample is to left. Photograph is courtesy of D.F. Toomey, University of Texas
Permian Basin. Thin section, approximately x 9