Pg. 13 (fig. 6), 24-30, fig. 1 (geol. map), fig. 7. Alacran Mountain Formation; name applied to uppermost formation in [Hueco] group. Except for the 122-foot Deer Mountain red shale member in lower part, formation consists of light-olive-gray and olive-gray medium- and thick-bedded limestone; occasional very thick bedded units are massive cliff formers. Composite thickness about 622 feet; upper 220 feet not exposed at type section and reference section designated. Conformably overlies Cerro Alto limestone (new). Contact is one of gradual transition. Upper contact is everywhere one of disconformity, upper beds of formation having been removed by erosion. Overlain by unconsolidated sediments of Quaternary age. Wolfcamp-Leonard boundary, marked by appearance of SCHWAGERINA CRASSITECTORIA - S. FRANKLINENSIS fauna, falls within formation about 80 feet above last appearance of PSEUDOSCHWAGERINA.
Type section: southwest side of Alacran Mountain, a small mesa in central part of Hueco Mountains, Hudspeth Co., TX.
Reference section: fault-block exposure south of Menzies Ranch headquarters, also in central part of Hueco Mountains.

Source: US geologic names lexicon (USGS Bull. 1350, p. 9-10).