Cretaceous stratigraphy and biostratigraphy, Cooke's Range, Luna County, New Mexico
— Spencer G. Lucas, Barry S. Kues, Steven N. Hayden, Bruce D. Allen, Kenneth K. Kietzke, Thomas E. Williamson, Paul Sealey, and Randy Pence

Cretaceous strata in the Cooke's Range pertain to the Sarten and Mancos formations. The Sarten Formation is at least 107 m of sandstone, siltstone and minor conglomerate and limestone that disconformably overlies the Lower Permian Abo Formation. The Mancos Formation (formerly Colorado Shale) is as much as 64 m of siltstone, shale, limestone and minor sandstone that disconformably overlies the Sarten Formation. Three intervals in the Sarten Formation produce marine mollusc fossils. The lowest interval, about 15 m above the base, is equivalent to the late Albian Duck Creek Formation of Texas. The middle interval is latest Albian, and the youngest Sarten assemblage, from the upper 2 m of the formation, includes taxa of early Cenomanian age, equivalent to the Del Rio-Buda sequence of Cerro de Cristo Rey and Texas. The overlying Mancos Formation contains late Cenomanian-early Turonian ammonites, bivalves and selachian teeth indicating close correlation with the Greenhorn Limestone of the Western Interior. The Sarten and Mancos also contain moderately diverse microfossil (foraminiferan and ostracode) faunas.