First used as one of eight formations in the Sierra de Los Lamentos, northern Chihuahua, MX. The lower four formations (Angela, Los Lamentos, San Vicente, and Bufa limestones) are separated from the upper four formations (Sonora, Tlaxcala, Buena Suerte, and Triste limestones) by the Sonora thrust fault. It is possible that the formations above the Sonora fault are simply a repetition of the section below the fault. Type not designated; name attributed to F. L. Ransome, derivation not stated. Is base of section in study area. Underlies Los Lamentos limestone. Is locally referred to as "Blue Limestone." Is fine-grained limestone, breaks with rough conchoidal fracture, is relatively free of later veins of calcite, and is sparingly fossiliferous. Lowest part is thin-bedded limestone; upper beds are thicker and massive. Poorly preserved fossil sponges and foraminifers noted. Is 500+ ft thick. Is correlated (together with overlying Los Lamentos and San Vicente limestones) with the Trinity group of the Comanche series on basis of fossil fauna. Age is [Early] Cretaceous.

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