Earliest Wolfcampian (Permian) Leaf Fossils from Glass Mountains, Brewster County, Texas: A Preliminary Report

Karen Quick, G. G. Gibson

Permian Wolfcampian carbonate and siliciclastic strata exposed in the Glass Mountains, Brewster County, Texas, have been designated as the North American standard section for the Lower Permian Series. Superbly preserved marine invertebrate faunas from this area have been studied by several workers, are well-illustrated in the literature, and have provided a basis for regional correlation of marine strata.

Recent discoveries of abundant leaf fossils from formations containing these invertebrates, in this case the lowermost Permian Neal Ranch Formation of the Glass Mountains: (1) provide documentation of the oldest Permian flora known in the United States, (2) enable establishment of correlations between marine and nonmarine lower Wolfcampian strata in the southwestern United States, (3) clarify the Early Permian paleogeography of west Texas, and (4) have revealed several new floristic species and perhaps genera.

The Neal Ranch Formation, which immediately overlies the long-disputed Pennsylvanian-Permian boundary, has yielded a diverse flora of leaf impressions seeds from four shale intervals in a largely carbonate section that contains abundant marine invertebrates. In addition, poorly preserved plant material has been recovered from one locality in the controversial boundary unit, the Uddenites shale.

Limited excavation has so far revealed a flora dominated by conifers. Walchia is represented by at least two species and is more abundant than Gomphostrobus. Several species of pecopterids are present, with sphenopsids, taeniopterids, neuropterids, and odontoperids occurring less commonly. A few fragmentary specimens displaying a callipterid-like foliage have been collected as well as several types of seeds.

This flora appears to correspond to flora zone 13 of Read and Mamay, thus correlating with the basal portion of the nonmarine Abo Formation of New Mexico and the Wichita Group of north-central Texas. The Neal Ranch flora thus provides a correlation link between these nonmarine units and the marine units of West Texas.

AAPG Search and Discovery Article #91043©1986 AAPG Annual Convention, Atlanta, Georgia, June 15-18, 1986.