Pre-Marine Isotope Stage 2 glacial activity around the Nevado de Chañi massif in the Central Andes of Argentina and paleoclimate implications

Abstract

We describe and analyze the glacial geomorphology and new ¹⁰Be cosmogenic surface exposure ages from moraines deposited before Marine Isotope Stage (MIS) 2 around Nevado de Chañi (24°4′ S, 65°45′ W), a north–south-trending massif located in the arid subtropical mountains of northwestern Argentina. We combine these data with previously published ages in order to establish a glacier chronology around the massif and the central Andes. The results show at least three phases of glacier expansions occurred before the global Last Glacial Maximum, (i) during MIS 6, (ii) close to the transition from MIS 4 to MIS 3, and (iii) during mid-late MIS 3. Based on a comparison of the timing of glacier advances with other glacial and paleoclimatic proxies elsewhere, we infer that glaciers grew in this arid region of the subtropical Andes during periods of reduced temperatures and wetter conditions, ultimately due to intensification of the South American Summer Monsoon. In contrast, during MIS 5 no glacial activity was recorded around the massif, and we infer that even if wetter conditions prevailed in the region the temperature was not sufficiently low to support glaciations.