Circular 208—Latest Pennsylvanian and earliest Permian fusulinid biostratigraphy, Robledo Mountains and adjacent ranges, south-central New Mexico

By Gregory P. Wahlman and William E. King, 2002, 32 pp.

Latest Pennsylvanian and earliest Permian fusulinid foraminifera from the Robledo, Doña Ana, and southern San Andres Mountains, Doña Ana County, south-central New Mexico, are described, and their biostratigraphic significance and correlation are discussed. New collections of fusulinids from the Bursum formation-equivalent and lower Hueco member contain a few additional species not previously reported from the area and provide better material for some other previously reported species. Descriptions of the following species from the new collections are give: Leptotriticites aff. L. gracilitatus Skinner and Wilde, L. sp. A., Schwagerina andresensis Thompson, S. sp. A., Pseudofusulina robleda Thompson, Pseudoschwagerina morsei Needham, P. cf. P. uddeni (Beede and Knicker), P. texana Dunbar and Skinner, and P. texana ultima Dunbar and Skinner.

The Robledo Mountains contain one of the most continuous marine carbonate sections through the Pennsylvanian–Permian boundary interval in the southwest United States of America, and therefore it has potential significance as a reference section for correlation of the new international Carboniferous–Permian boundary from Eurasia to North America. The newly proposed Pennsylvanian-Permian boundary is designated the Robledo Peak section at the Bursum-Hueco contact, which is placed at the top of a sandy limestone interval that lies above the occurrences of Leptotriticites hughensis, L. glenensis, L. aff. gracilitatus, L. sp. A., Pseudofusulina robleda, and Schwagerina grandensis, and below the basal occurrences of Pseudoschwagerina morsei, P. taxana, P. texana var. ultima, P. cf. P. uddeni, Schwagerina andresensis, and Leptotriticites tumida. The stratigraphically higher fusulinid assemblage correlates well to the faunas of the Neal Ranch Formation (Nealian) of the Wolfcampian stratotype section in the Glass Mountains of west Texas.