Late Pleistocene moraines of the Plata range (32ºS), Central Andes.

MOREIRAS S.M.; CARRETIER S.; JEANNERET P.; VERGARA I.

Encuentro; Meeting of INQUA Project 1311.; 2015

We present the first numerical datings of glacial deposits preserved in the eastern slope of the Plata Mount (6,200 m asl). The studied moraines are distributed along three different valleys named Vallecitos, Angostura, and Las Mulas, respectively. Only one moraine was identified for the former where no blocks could be dated as ski facilities and a route were built on the disturbed moraine. Two glacial advances were established for the other valleys. They were called as Angostura I and Angostura II; while the Loma de los Morteritos I and the Loma de los Morteritos II were recognised along the Las Mulas valley. In both cases, those advances are preserved at similar altitude in respective valleys. Quartz veins of metamorphic boulders located on the top of identified moraine deposits were sampled for terrestrial cosmogenic nuclide dating (Be10). Obtained ages range in Late Pleistocene matching among them and fitting very well with local stratigraphy. The Loma de los Morteritos moraine II located at 3,000 m. asl resulted 39 ky; while ages of 17 and 25 Ky were found for the Angostura II deposit (~3,300 m asl). Even new datings represent a minimum age for these glacial advances, they contrast with age assigned to these diamictons by relative dating techniques in previous early studies of the 80´s what definitively improves knowledge about Quaternary stratigraphy of the Central Andes. New findings support the occurrence of two Late-Pleistocene glacial advances, and an older one, in the Blanco River valley (Fig. 1).