Chronology of Late Pleistocene glacial advances in a Mount Mercedario catchment, Subtropical Andes of Argentina (32° S)

Abstract

Glacial fluctuations leave distinct imprints on the landscapes of mountain environments, such asmoraines and outwash terraces, that allow the reconstruction of past environmental changes. Unraveling theenvironmental history of the valleys of the Subtropical Andes of Argentina poses challenges due to the complexinterplay of various surficial processes driven by both climatic and tectonic forces, which affects the preservation ofglacial deposits. Consequently, there are few studies on past glaciations in this region compared to the rest of theAndes. This study focused on the lower section of the Blanco River Basin and the piedmont of the Frontal Cordillerain the south of San Juan Province, Argentina. A comprehensive geomorphological map of glacial landforms wascreated, along with sedimentological studies of outwash terraces. Additionally, numerical ages were obtained forboth landforms using terrestrial cosmogenic nuclides for moraine boulders and luminescence dating for sandy layersin the outwash terraces. Our findings reveal at least two glacial advances since the Last Glacial Maximum (LGM),each associated with distinct outwash levels. The Río Blanco Advance occurred during the LGM, and the LagunaAdvance is assigned to the late stages of the LGM, both with their corresponding outwash terraces. Additionally, theAmarillo Advance is believed to have occurred during the Holocene period and an older Marine Istope Stage 5 dnamed Guanaquito Advance. The provided data add valuable numerical information about glacial fluctuations sincethe LGM and also reveal the impact of glacial downwasting on piedmont landforms.