The stratigraphic framework for the Mogollon-Datil volcanic field has undergone many revisions. The Datil Formation was originally defined by Winchester in 1920 to include all the extrusive units from the field. The Datil Formation was later promoted to group rank with the addition of some related sedimentary formations, such as the Baca Formation"Tertiary and Quaternary: Baca Formation" Open File Report 94 (1977), New Mexico Bureau of Geology & Mineral Resources, page 88Chapin, Charles E. et al. (1978) "Exploration framework of the Socorro geothermal area, New Mexico" pp. 114–129 In Chapin, Charles E. et al. (editors) Field guide to selected cauldrons and mining districts of the Datil-Mogollon volcanic field Special Publication NO. 7, New Mexico Geological Society, Winchester, Dean E. (1920) Geology of Alamosa Creek Valley, Socorro County, New Mexico with special reference to the occurrence of oil and gas U.S. Geological Survey Bulletin 716-A, and the Spears Formation. The base of the group, as originally defined, rests unconformably on the Mesaverde Formation, and the series is succeeded by the Popotosa Formation of the Santa Fe Group.
