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 as moraines and outwash terraces, that allow the reconstruction of past environmental changes. Unraveling the environmental history of the valleys of the Subtropical Andes of Argentina poses challenges due to the complex interplay of various surficial processes driven by both climatic and tectonic forces, which affects the preservation of glacial deposits. Consequently, there are few studies on past glaciations in this region compared to the rest of the Andes. This study focused on the lower section of the Blanco River Basin and the piedmont of the Frontal Cordillera in the south of San Juan Province, Argentina. A comprehensive geomorphological map of glacial landforms was created, along with sedimentological studies of outwash terraces. Additionally, numerical ages were obtained for both landforms using terrestrial cosmogenic nuclides for moraine boulders and luminescence dating for sandy layers in 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 Laguna Advance is assigned to the late stages of the LGM, both with their corresponding outwash terraces. Additionally, the Amarillo Advance is believed to have occurred during the Holocene period and an older Marine Istope Stage 5 d named Guanaquito Advance. The provided data add valuable numerical information about glacial fluctuations since the LGM and also reveal the impact of glacial downwasting on piedmont landforms.