The Geste Formation (Spanish: Formación Geste) is a geologic formation of the Puna Plateau in the western Salta Province and northern Catamarca Province of the Argentine Northwest, northwestern Argentina. The Geste Formation has provided a faunal assemblage of vertebrates unique for the Argentine Northwest, with several groups of mammals, most notably the only Paleogene interatheres of northwestern Argentina, reptiles and frogs. Only partly they correspond to other fossiliferous formations in the area; the upper part of the and the .