Radiometric dating gives it an age of 1.85 million to 72 thousand years, corresponding to the Pleistocene epoch.

This has produced a long-lived volcanic field, with the earliest eruptions beginning at least 13 million years ago in both the northern (Polvadera Group) and southern (Keres Group) portions of the volcanic field.

[4] High-silica eruptions of the Tewa Group began about 1.85 million years ago (Ma) and continued almost to the present day.

It overlies the Santa Fe, Keres, and Polvadera Groups to the east and south of the caldera and older rocks ranging in age from Paleoproterozoic to Permian to the west and north.

[8] It includes the most recent eruptions in the Jemez Mountains, ending with the Banco Bonito flow.

Ross adopted Grigg's nomenclature in 1969 as part of their work establishing the stratigraphy of the Jemez Mountains, but proposing some further subdivisions of formations and members.