Contents lists available at ScienceDirect Journal of South American Earth Sciences journal homepage: www.elsevier.com/locate/jsames A Chasicoan (late Miocene) vertebrate assemblage from Cerro Azul Formation, central Argentina. Geomorphological and biochronological considerations C.I. Montalvo a,∗ , R.L. Tomassini b , R. Sostillo c , E. Cerdeño d , D.H. Verzi e , G. Visconti a , A. Folguera f , G.I. Schmidt g a Facultad de Ciencias Exactas y Naturales, Universidad Nacional de La Pampa, Uruguay 151, 6300, Santa Rosa, Argentina b INGEOSUR, Departamento de Geología, Universidad Nacional del Sur - CONICET, Avenida Alem 1253, 8000, Bahía Blanca, Buenos Aires, Argentina c CONICET, Facultad de Ciencias Exactas y Naturales, Universidad Nacional de La Pampa, Uruguay 151, 6300, Santa Rosa, Argentina d Paleontología, IANIGLA, CCT-CONICET Mendoza, Avda. Ruiz Leal s/n, 5500 Mendoza, Argentina e Sección Mastozoología, División Zoología Vertebrados, Facultad de Ciencias Naturales y Museo, Universidad Nacional de La Plata, Paseo del Bosque s/n, 1900 La Plata, Buenos Aires, CONICET, Argentina f Instituto de Geología y Recursos Minerales, Servicio Geológico Minero Argentino, 1650 San Martín, Argentina g Laboratorio de Paleontología de Vertebrados, Centro de Investigaciones Científicas y Transferencia de Tecnología a la Producción (CICYTTP-CONICET UADER-Provincia de Entre Ríos), Materi y España, E3105BWA, Diamante, Entre Ríos, Argentina ARTICLEINFO Keywords: Faunal assemblage Biochronology Cerro Azul Formation Neogene Central Argentina 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 as- semblages 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. 1. Introduction Late Cenozoic outcrops in La Pampa Province (central Argentina) are mainly represented by deposits of the Cerro Azul Formation, which are largely extended in the center and east of this province, as well as in southwestern Buenos Aires Province and southeastern Mendoza Province (Folguera and Zárate, 2009). This formation has provided interesting faunal assemblages, at different localities, assigned to the late Miocene (Verzi et al., 2008; Sostillo et al., 2014; Montalvo et al., 2016; among others). Recent biostratigraphical and biochronological interpretations, based on anagenetic sequences in octodontontoid ro- dents (Chasichimys–Xenodontomys, Neophanomys and Reigechimys), suggest the presence of both Chasicoan and Huayquerian faunas at different levels of the Cerro Azul Formation (Verzi, 1999; Verzi et al., 2003, 2004; 2008; Sostillo et al., 2014; Montalvo et al., 2016). As there is no stratigraphic superposition among the deposits of different lo- calities, relationships among fossiliferous levels were established through the polarity evidenced by the evolutionary stage of the chronomorphs (sensu Martin, 1993) integrating these anagenetic lineages. One of the localities with outcrops of Cerro Azul Formation in La Pampa Province is Cerro La Bota. It is placed at the southwestern limit of the Pampa Central Block (Folguera and Zárate, 2011, 2018; see below). The recovered fauna was preliminarily assigned to the Chas- icoan based on the presence of the Ctenomyidae rodent Chasichimys bonaerense, representing the oldest section of the Cerro Azul Formation (Verzi, 1999; Verzi et al., 2008). In this contribution, we present an updated revision of the vertebrates from Cerro La Bota, as well as new geomorphologic and sedimentological interpretations of the Cerro Azul Formation in the area. https://doi.org/10.1016/j.jsames.2019.102218 Received 10 April 2019; Received in revised form 24 May 2019; Accepted 25 May 2019 ∗ Corresponding author. E-mail address: cmontalvo@exactas.unlpam.edu.ar (C.I. Montalvo). Journal of South American Earth Sciences 95 (2019) 102218 Available online 30 May 2019 0895-9811/ © 2019 Elsevier Ltd. All rights reserved. T