New Mexico Geological Society Annual Spring Meeting — Abstracts

A small limestone outcrop 5 km northwest of the Tres Hermanas Mountains in southwestern New Mexico was studied as part of a project to correlate the stratigraphic and depositional settings of Wolfcampian limestone in the Florida Mountain region. Samples were collected from the 23 m section at 1.7 m intervals; additional samples were taken at lithologic changes. Thin sections of 24 samples were analyzed and classified according to Dunham (1962) and assigned facies belts according to Wilson (1975). Dominant bioclasts include tubular foraminifera, gastropods, ostracods and algae (stromatolite, phylloid, red, and dasyclad). Minor bioclasts include echinoderms, bryozoans, brachiopods and fusulinids. Unfortunately the fusulinids are sparse and mostly neomorphosed. Most bioclasts are encrusted by tubular foraminifera or less abundantly, coated by algae. The section is composed primarily of packstones, but a few wackestones, grainstones and stromatolite boundstones are also present.

Depositional environments varied from shallow, restricted circulation on a marine platform (FB 8 ) to a shallow, open marine lagoonal facies (FB 7). The base of this section is composed of stromatolite boundstones and abundant tubular foraminifera, which represent a shallow, restricted environment. These grade upward into a restricted lagoonal environment dominated by gastropods, tubular foraminifera and ostracods. The top of the section shows the greatest diversity of fauna, containing echinoderms, bryozoans and brachiopods as well as tubular foraminifera, ostracods, gastropods, phylloid algae and dasyclad algae. The fauna, particularly the fusulinids and the abundance of tubular foraminifera. indicate this section is probably Wolfcampian and equivalent to the Hueco and/or Colina Formations.