zzzzzPg. 148. Cooks formation of El Paso group [author does not capitalize rank terms; however, units are considered formal]. Name applied to first endoceroid zone. Younger than Big Hatchet formation (new) and older than Victorio formation (new). Age is Early Ordovician (middle Canadian; Demingian). Canadian treated as a system in this report. Author states that his philosophy of nomenclature is contrary to "the present fashion of delimiting formations on lithology alone." The resulting proposed divisions of the El Paso Group are thus "a succession of strata and faunas."
Type section is in northern end of Cooks Range [Luna Co., NM]. Named from the defunct town of Cooks, 12 mi north of Deming, which is as reasonably close to the type section in the northern end of the Cooks Range as a named place can be found.

Source: US geologic names lexicon (USGS Bull. 1350, p. 169); supplemental information from GNU records (USGS DDS-6; Denver GNULEX).