Named for Cowboy Spring, SE1/4 sec 13, T31S, R18W, Hidalgo Co, NM in Pedregosa basin, where the formation has its only exposure; this is designated the type locality. Geologic map. Consists chiefly of limestone cobble conglomerate, the base of which is conformable and transitional with Mojado Formation--sandstone of Mojado and conglomerate of Cowboy Spring interfinger gradationally within the transition zone. Limestone conglomerate beds are separated by beds of sandstone, shale, claystone, and tuff. Because of greater abundance and resistance, conglomerate is well exposed; other rocks are present in erosional troughs and are mostly concealed. Limestone conglomerate is massive, thick-bedded, and resistant, with subrounded cobbles in a red, calcareous, argillaceous matrix. Interbedded sandstone is mostly red and arkosic, some is argillaceous, and most is weakly cemented; beds are thin. Shale is mostly bright-red; some is gray and green. Claystone is gray, unconsolidated, unstratified, and poorly exposed. A 20-ft bed of red, purple, and white latite porphyry tuff exposed. Is overlain with angular unconformity by Timberlake Fanglomerate (new) of Tertiary age. Owing to angular unconformity, original thickness is unknown; more than 1,000 ft of unit is exposed. Is of Early and Late Cretaceous age. No fossils found. Shown on geologic map.

Source: GNU records (USGS DDS-6; Denver GNULEX).

Is conglomeratic formation in Animas Mountains, Hidalgo Co, NM in Pedregosa basin. Overlies Mojado Formation (Lower and Upper Cretaceous) with parallel but disconformable contact. May be equivalent to Skunk Ranch Conglomerate (late Late Cretaceous age) in Little Hatchet Mountains. May be partly equivalent to Fort Crittenden Formation (Campanian) in Santa Rita Mountains-Canelo Hills-Huachuca Mountains area, AZ. [See fig. 5 for regional correlations.] Age changed from late Early Cretaceous or early Late Cretaceous (Zeller, Jr., and Alper, 1965) to late Late Cretaceous (Campanian) on basis of stratigraphic position dating and correlation with Skunk Ranch.

Source: GNU records (USGS DDS-6; Denver GNULEX).

Present in the Animas Mountains, Hidalgo Co, NM in Pedregosa basin. No fossils found but is believed to be very late Albian age because it intertongues with the underlying Mojado Formation and because lithology suggests rapid deposition. Could be very early Cenomanian age.

Source: GNU records (USGS DDS-6; Denver GNULEX).

Cowboy Spring Formation of Timberlake Fanglomerate of Zeller and Alper (1965) combined into Cowboy Spring-Timberlake Conglomerate because no contact or lithologic break is evident. Unconformably overlies Mojado and U-Bar Formations. Is of Tertiary age.

Source: GNU records (USGS DDS-6; Denver GNULEX).