Depositional sequences, Fusulinid zones
The lower Leonardian (Lower Permian) Hess Limestone in the eastern part of the Glass Mountains, West Texas, forms a high, well-exposed escarpment of repetitious, shallow-water, platform limestone facies for about 35 km. The strike of the outcrops cuts the strike of depositional facies at relatively low angle so that the actual width of the carbonate platform, from its marginal rim to shore facies, was probably less than 10 km (Figs. 1, 2). At the platform margin, the Hess Limestone passes abruptly into coarse, conglomeratic slope deposits that form the Skinner Ranch Formation. The pebbles, cobbles, boulders, (some the size of a small house) and other clastic debris in this facies include both reworked limestones from older Paleozoic formations and redeposited penecomptemporaneous carbonate blocks and pieces from the outer margin and rim facies of the Hess platform. Many previously described fossils faunas attributed to the Skinner Ranch Formation include a mixture of reworked older faunas (especially from the Lenox Hills, Neal Ranch, and Gaptank Formations), penecontemporaneous fossils redeposited from the Hess platform and rim, and in situ faunas of the Skinner Ranch slope facies. The foraminifers of the platform are relatively common, but they have a low species diversity. Those of the slope facies are more diverse, however, as with the other faunas, the foraminifers include a mix of platform, margin and rim species, upper slope species, and a large number of reworked specimens from older deposits, both in cobbles and pebbles and as individual specimens reworked from shales. To the west, the Skinner Ranch facies thins within a short distance, less than 2 or 3 kilometers, and passes into a thin, dark, turbiditic basinal facies. Similar platform, slope, and basin lithologic facies and topographic depositional relief are common in strata of equivalent age around the margin of most of the Permian Basin in western Texas and southeastem New Mexico (Mazzullo and Reid, 1989; Reid and others, 1989).
Cushman Foundation for Foraminiferal Research
Special Publication 36
Required Publisher's Statement
Permission was granted for publication of this article in Western CEDAR by the editor of the Journal of Foraminiferal Research.
This article was published in Late Paleozoic Foraminifera: Their Biostratigraphy, Evolution, and Paleoecology and the Mid-Carboniferous Boundary. Eds. Charles A. Ross, June R. P. Ross, and Paul L. Brenckle. Cushman Foundation for Foraminiferal Research, 1997, Special Publication No. 36.
Ross, Charles A. and Ross, June R. P., "Hessian (Leonardian, Middle Lower Permian) Depositional Sequences and Their Fusulinid Zones, West Texas" (1997). Geology Faculty and Staff Publications. 63.