Abstract

General inaccessibility to ranches during many of the years since P. B. King’s (1965) last work in the Sierra Diablo has hampered the achievement of a modern synthesis of the regional algeologic setting. Recently Starcher (1992), working on a Master’s thesis, has undertaken a study of the Wolfcampian (Hueco Limestone) and Fitchen (1994), working on his Ph. D. dissertation, the Leonardian (Bone Springs and Victorio Peak limestones). They, together, have had the opportunity to unravel lower Permian stratigraphic relationships. Both of these workers have confined their efforts to Apache Canyon, near the north end of the Sierra Diablo. Here the canyon has cut deeply across the range to expose, essentially in dip section, thick sections of these stratigraphic units. This has provided a unique opportunity to apply sequence stratigraphic concepts in understanding complex depositional relationships.

Recently, the author has had the opportunity to examine thin sections of fusulinids provided by Starcher, from the Hueco Limestone, and Fitchen, from the Leonardian units, in Apache Canyon. Although some of this work is in a preliminary stage, enough is now known so that fusulinid biostratigraphic zones can be calibrated with depositional sequences (Fitchen and Starcher, 1992). Following such an approach, the surface stratigraphy can be matched to that of the subsurface, which commonly utilizes different formational names for mapping purposes.

Thus, in Apache Canyon, the Wolfcampian Hueco Limestone is divisible into two main biostratigraphic units, encompassing the Middle and Late Wolfcampian Stage. The Early Wolfcampian (Bursumian Stage of Ross and Ross, 1994) is not known to be present in the Sierra Diablo.

The Leonardian Bone Spring and Victorio Peak formations, in Apache Canyon, are divisible into three biostratigraphic units, covering all except possibly the very youngest Leonardian. Utilizing Fitchen’s field work and the fusulinid zonation, subsurface units, including the Abo, Lower Clearfork, Tubb, Middle and Upper Clearfork are recognizable.