Refined Fusulinid Biostratigraphic Zonations of Wolfcampian and Lower Leonardian Strata in Permian Basin

A. M. Reid, S. T. Reid, S. J. Mazzullo, S. C. Robbins

Stratigraphic ranges, relative generic abundances, and evolutionary changes in the skeletal morphology of fusulinids form the basis for a refined subdivision of Wolfcampian and lower Leonardian strata in the subsurface Permian basin. The Wolfcampian Series is recognized by the occurrence of various Schwagerina sp. (including primitive forms and those that show a progressive evolution from minor to intensely fluted septae and progressive changes in shell size and shape), Paraschwagerina and Pseudoschwagerina, Monodiexodina, Triticites, Leptotriticites, "Triticites-Schwagerina," and Schubertella sp. (S. kingi and other elongate forms). The section is divided into a tripartite sequence of lower (with three subunits), middle (with two subunits), and upper (with two subunits) Wolfcampian z nes. The lower Leonardian Series is recognized by the occurrence of Parafusulinia, various Schubertella sp. (including S. melonica), and advanced Schwagerina sp. (with and without axial fill and phrenotheca). The section is divided into a tripartite sequence of lower, middle, and upper subunits of the lower Leonardian.

The present biostratigraphic zonations are widely recognized throughout the subsurface Permian basin. Our zonations generally relate to those of Hollingsworth and Wilde in the following manner: approximately the lower half of our lower Wolfcampian is equivalent to the "Bursum;" the middle and upper part of the lower Wolfcampian and basal portion of the middle Wolfcampian are included in the "Lower Hueco;" the section from the basal middle Wolfcampian to the top of the upper Wolfcampian is included in the "Upper Hueco" of Hollingsworth, the upper part of which (our upper Wolfcampian) being the Monodiexodina linearis assemblage subzone of Wilde. The tripartite lower Leonardian is equivalent to the "Lower Leonard" of Hollingsworth, and the Schwagerina crassitectoria assemblage subzone of Wilde.

AAPG Search and Discovery Article #91026©1989 AAPG Southwest Section, March 19-21, 1989, San Angelo, Texas.