New Miocene mammal assemblages from Neogene Manantiales basin, Cordillera Frontal, San Juan, Argentina

LÓPEZ, GUILLERMO M.; VUCETICH, MARÍA G.; CARLINI, ALFREDO A.; BOND, MARIANO; PEREZ, M. E.; CIANCIO, MARTÍN R.; PEREZ, D. J.; ARNAL, M.; OLIVARES, A. I.

Cenozoic Geology of Central Andes of Argentina

SCS Publisher

Lugar: Salta; Año: 2011; p. 211 - 226

The discovery of abundant fossil mammals from two different levels of the lowest third of theChinches Formation (Manantiales basin) located in Cordillera Frontal of San Juan, between32°30´ and 33°S, is reported. These synorogenic Miocene deposits were deposited by thestructural evolution of Cordón de La Ramada fold and thrust belt. Two diverse fossil mammalassemblages have been recognized, one from the lowest bearing horizon, informally named“Chinches bearing level" (CBL), and other, stratrigraphically higher, informally named “LasHornillas bearing level” (LHBL). Marsupials, Xenarthra (Cingulata and Tardigrada),Notoungulates (four families), Litopterns and six groups of rodents are represented in bothmammal assemblages. The presence of taxa recorded only in sediments referred to theSantacrucian (e.g. Peltephilus, Nesodon, Hegetotherium mirabile, Eocardia montana andEocardia excavata), and others with evolutionary degree comparable to that of Santacruciantaxa (e.g. Stenotatus, Hapalops, Protypotherium, Theosodon and mesotheriines) suggest bothassemblages may be referred to the Santacrucian South American Land Mammal “Age” (lateearly Miocene). This temporal reference matches with studies of fission–track andmagnetostratigraphy, and sedimentological data of this sequence. The latitudinal intermediatelocation together with the particular taxonomic composition of these assemblages may providethe clue to understand the differences between Miocene faunas from Patagonia and theAltiplano (Chile and Bolivia). As well, these assemblages are a new important source ofinformation for the comprehension of the phyletic and geographic relationships of severaltaxa, and the paleoenvironmental changes associated with the uplift of the Andes.