Page 447 - Carbonate Facies in Geologic History

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Plate XIII. Restricted Marine Microfacies

(A) Peloidal packstone with fenestral fabric due to desiccation of pelleted lime
mudstone, also standard microfacies 16 and facies PM-12, Chapter VIII. Calci-
spheres (probably fruiting cases of algae) are scattered in the sediment. The fenes-
trules contain crystalline calcite with a void-filling pattern. Aggregation of such
semi-hardened peloids with coating and micritization of the outside of such com-
posite masses results in creation of grapestone lumps. The abundance of the latter
in peloidal sparite sediment defines standard microfacies 17. Indeed, a spectrum
exists from pelleted mudstone, to pellet packstone-grainstone, to grapestone pel-
sparite (grainstone). This sample PR-ll shows an intermediate stage and is from
the backreef of the Permian Reef Complex, Guadalupe Mountains, Tansill For-
mation, in Rocky Arroyo, 30 km northwest of Carlsbad, New Mexico. Thin sec-
tion, x 13
(B) Foraminiferal, dasyc1adacean grainstone-packstone. See also Plate VI-A,
standard microfacies 18. This sample is a packstone of Mizzia (?) a dasyc1adacean,
and miliolid-like tubular foraminifera, and a few shell fragments; from the
Permian of Yugoslavia. Photograph courtesy of D.F. Toomey, University of
Texas Permian Basin. Such coarse grainy sediment is commonly found in bars
and shoals heaped up by tidal currents in shallow lagoons and bays and is
common throughout the geologic record. Thin section, x 15