The Cerro Rajado Formation, La Rioja Province, Argentina

Abstract

?The Cerro Rajado Formation, La Rioja Province, Argentina?. This Formation, of the Ischigualasto-Ischichuca Basin, of West-Central Argentina, is a lithoestratigraphic unit enclosed by two unconformities, the lower one with the Triassic substratum and the upper one with Tertiary Formations, which could belong to the Catan-Lil and Mirano Tectonic Cycles respectively. The lower unconformity is erosive and covers a low relief of Los Colorados Formation (Agua de la Peña Group) nearby a somewhat higher one, composed by Crystalline Basement (Valle Fértil Group). The outcropping sedimentary rocks consist of fine conglomerates with metamorphic angular clasts (distal piedmont facies), associated to silty sandstones, very finely to laminarly stratified and salted (playa deposits). The sedimentation is typical of an arid to semiarid valley environment.