New Mexico Geological Society Annual Spring Meeting — Abstracts

In 1869 Hayden originally applied the term "Santa Fe marls" to the "recent marls and sands which seem to occupy the greater portion
of the valley of the Rio Grande above and below Santa Fe." Subsequently, Darton (1922) and Denny (1940) recognized the Santa Fe Formation with its type area being lithe region north of Santa Fe, New Mexico, between the Sangre de Cristo and Jemez Mountains,"
i.e., the Espanola basin. Baldwin (1956) and Spiegel and Baldwin (1963) raised the term Santa Fe to group status, and the term Santa Fe Group has long been used by most geologists to include all Upper Cenozoic (Miocene and younger) rocks in the Rio Grande rift.

Such broad application of the term Santa Fe Group needs to be reconsidered for two reasons: 1. Santa Fe Group as presently used refers to a very heterogenous and diverse array of sedimentary and volcanic rocks deposited in different basins under a wide range of structural and volcanic settings. 2. With minor exceptions, rocks of the Santa Fe Group in each of the many basins of the Rio Grande rift have been formally divided into formations and members. These two observations suggest that the term Santa Fe Group either is misleading (it creates a false impression of lithologic homogeneity for rocks in the Rio Grande rift) or is unnecessary (more precise stratigraphic terms are available for virtually all rocks in the Rio Grande rift). In light of this, either the term Santa Fe Group should be abandoned or its usage should be restricted to refer to rocks in its type area.