Incapillo is found on a crust thick, among the thickest in volcanic regions of the Earth. Several studies by Suzanne Mahlburg Kay and others indicate that trends in the isotope ratios are because of a thickening crust and increased contribution thereof to the magmas. At the latitude of Incapillo, the northern Antofalla terrane borders the Cuyania terrane, both of which were attached to South America during the Ordovician but are of different provenance.