New Miocene mammal assemblages from Neogene Manantiales basin, Cordillera Frontal, San Juan, Argentina. En "Cenozoic Geology of the Central Andes of Argentina" (J.A. Salfity y R.A. Marquillas, Eds.)

LÓPEZ, G.M., VUCETICH, M.G., CARLINI, A.A., BOND, M., PÉREZ, M.E., CIANCIO, M.R., PÉREZ, D.J., ARNAL, M., OLIVARES, A.I.

The Geological Society of America Special Paper

GSA

Lugar: Washington, DC USA; Año: 2010

0072-1077

The discovery of abundant fossil mammals from two different levels of the lowest third of the Chinches Formation (Manantiales basin) located in Cordillera Frontal of San Juan, between 32°30´ and 33°S, is reported. These synorogenic Miocene deposits were deposited by the structural evolution of Cordón de La Ramada fold and thrust belt. Two diverse fossil mammal assemblages have been recognized, one from the lowest bearing horizon, informally named “Chinches bearing level" (CBL), and other, stratrigraphically higher, informally named “Las Hornillas bearing level” (LHBL). Marsupials, Xenarthra (Cingulata and Tardigrada), Notoungulates (four families), Litopterns and six groups of rodents are represented in both mammal assemblages. The presence of taxa recorded only in sediments referred to the Santacrucian (e.g. Peltephilus, Nesodon, Hegetotherium mirabile, Eocardia montana and Eocardia excavata), and others with evolutionary degree comparable to that of Santacrucian taxa (e.g. Stenotatus, Hapalops, Protypotherium, Theosodon and mesotheriines) suggest both assemblages may be referred to the Santacrucian South American Land Mammal “Age” (late early Miocene). This temporal reference matches with studies of fission–track and magnetostratigraphy, and sedimentological data of this sequence. The latitudinal intermediate location together with the particular taxonomic composition of these assemblages may provide the clue to understand the differences between Miocene faunas from Patagonia and the Altiplano (Chile and Bolivia). As well, these assemblages are a new important source of information for the comprehension of the phyletic and geographic relationships of several taxa, and the paleoenvironmental changes associated with the uplift of the Andes.