This lexicon includes the names of all Cenozoic lithostratigraphic units in New Mexico formally and informally proposed before 1981. It also includes Cenozoic chronostratigraphic units defined in New Mexico. Previous lexicons by Elston (1976), Keroher and others (1967), Lochman-Balk (1959, 1964, 1965, 1967), Lochman-Balk and Bruning (1971), Maclachlan (1976), Northrop (1973), Wilmarth (1938) and Wilson and others (1957) have aided in the compilation of this lexicon.
Each entry begins with the unit name; underlined names are those that have been formally recognized, at one time or another, by the United States Geological Survey. Parenthetical insertions after the unit name give alternate usages (for example, Abiquiu Formation or Abiquiu Tuff) and/or indicate the member, formation, group or series in which the unit is (or was) included. Unit names in brackets are old, discarded names and more recently proposed names no longer in use.