The Cariblanco Formation, here named, consists of thin- to medium-bedded siltstone and sandstone that intertongues with massive conglomerate. Units of limestone, tuff, and lava in the formation are named, in order of decreasing age, the La Guaba Lava Member, the Hacienda Larga Tuff Member, the Jobo Dulce Limestone Member, the Pio Juan Limestone Member, and the Sabana Hoyos Limestone Member. Overlies the Robles Formation; underlies the Coamo Formation. Age is Late Cretaceous. The Hacienda Larga Member is indurated, massive to thick-bedded volcanic ash 100 m above the base of the Cariblanco.

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

The uppermost Sabana Hoyos Limestone Member is here removed from the Cariblanco Formation and is included as a member of the overlying Maravillas Formation. In the Coamo area the Cariblanco includes the La Guaba Lava Member near the base and the Jobo Dulce and Pio Juan Limestone Members in the upper part. The Hacienda Larga Tuff Member originally named in the Coamo quadrangle in the belief that it was a unique isochronous rock unit, has been shown to be merely a rather pure accumulation of a crystal tuff component of the matrix. Specific correlation of the crystal tuff mapped at Hacienda Larga south of the Rio Cuyon with the Hacienda Larga Member mapped north of the Rio Cuyon is not implied.

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