The area is largely covered by Cenozoic sediments and volcanic rocks, but in outcrops a number of older formations can be observed: Devonian-Carboniferous marine deposits (Zorritas Formation), pyroclastic rocks (La Tabla Formation), both of which reach thicknesses of over 2 kilometers , 300-280 million years old plutons, the Triassic sediment-volcanic Sierra Guanaco and the fluvial-lacustrine Sierra de Varas and the marine Rhaetian-Jurassic Profeta Formation.