New Mexico Geological Society Annual Spring Meeting — Abstracts

Ammonites are present in Lower Cretaceous strata of the Bisbee Group at only one location in the central Peloncillo Mountains, Hidalgo County, New Mexico: in Exogyra packstones and calcareous siltstones 6-12 m above the base of the Carbonate Hill Formation in the SW¼ SE¼ NE¼ SE¼ sec. 34, T24S, R21W. Gillerman (1958, NMBMMR Bulletin 57) first reported these ammonites, which now number 14 specimens stored in three places: the Natural History Museum of Los Angeles County (Gillerman's original collection), the New Mexico Museum of Natural History (our recent collections) and the private collection of Donald McGhee of Lordsburg, New Mexico, who owns the land at the ammonite locality.

The ammonites from the Carbonate Hill Formation represent the following taxa: Acanthoplites sp., Acanthoplites grandensis Scott (which is not Douvilleiceras), Acanthoplites hesper Stoyanow, Hypacanthoplites (=Immunitoceras) immunitus (Stoyanow), Hypacanthoplites sp., Stoliczkaia patagonica Stoyanow and "Sonneratia" fosteri Scott (which is neither Sonneratia nor Kazanskyella). These ammonites indicate that the lower part of the Carbonate Hill Formation encompasses the Kazanskyellaspathi Zone of late Aptian age. It thus is correlative with the "Quajote Member of the Lowell Formation" (=lower Mural Formation) in Arizona and the oyster-limestone member of the U-Bar Formation in the Big Hatchet Mountains.