A Chasicoan (late Miocene) vertebrate assemblage from Cerro Azul Formation, central Argentina. Geomorphological and biochronological considerations

Abstract

The Cerro Azul Formation, mainly extended in the center and east of La Pampa Province (Argentina), has provided interesting late Miocene faunal assemblages mostly assigned to the Huayquerian. However, other assemblages recovered from several localities were preliminarily assigned to the Chasicoan. One of them, based on the presence of the Ctenomyidae rodent Chasichimys bonaerense, was Cerro La Bota, placed at the southwestern limit of the Pampa Central Block. The revision of the vertebrate assemblage from this locality, as well as new geomorphologic and sedimentological interpretations of the Cerro Azul Formation in the area, confirms the previous assignation to the Chasicoan age. Cerro La Bota shares 18 taxa with Arroyo Chasicó Formation in Buenos Aires Province; several of them are mentioned for the first time for Cerro Azul Formation in La Pampa Province. Geomorphological data indicate that Cerro La Bota is included in a topographic step linked to the Valle Daza–Lonco Vaca fault that exposed the older levels of the Cerro Azul Formation in the area.