Holocene climate variability as reconstructed from 10Be dated glacial and periglacial phases in the Subtropical Andes

Despite major advances in paleoclimatology, key uncertainties remain regarding Holocene climate variability in the Southern Hemisphere, particularly concerning the evolution of the position and intensity of the Southern Westerly Winds (SWW) and their influence on high mountain cryospheric systems. The Subtropical Andes of Chile (30–35°S), located near the northern margin of SWW influence, offer an exceptional geomorphic record derived from glacial and periglacial ice in response to past climatic changes, and therefore suitable for reconstructing Holocene SWW variability.

Well-preserved glacial landforms, such as moraines, have been widely used to reconstruct past periods of increased moisture (e.g. Aguilar et al., 2022; Fernández-Navarro et al., 2023, 2024; García et al., 2024; Sagredo et al., 2017; Zech et al., 2017). In parallel, recent inventories show that the Subtropical Andes of Chile and Argentina host the most extensive periglacial belt in the Southern Hemisphere (Barcaza et al., 2017; DGA, 2022; Masiokas et al., 2020). Rock glaciers, indicative of sustained cold-ground and relatively arid conditions (Azócar & Brenning, 2010), therefore represent a major but still underutilized paleoclimatic archive. Although recent studies have demonstrated the potential of cosmogenic exposure dating of rock glaciers for paleoclimate reconstruction (e.g. Amschwand et al., 2021), this approach has remained unexplored in the Subtropical Andes until now.

Although glacial and periglacial landforms commonly coexist within the same catchments in the Subtropical Andes of Chile (e.g., Aguilar et al., 2022; Carraha et al., 2024), their temporal and morphostratigraphic relationships remain poorly constrained. Consequently, the timing and climatic drivers of glacial and periglacial phases are still mostly unknown (García et al., 2024; Jones et al., 2019), limiting our understanding of the Holocene paleoclimate and its cause. Here we present new ¹⁰Be cosmogenic exposure ages from moraines and surface blocks on multi-lobate rock glaciers in the Piedra Valley (30°S) to help constrain the timing and extent of periglaciaton of this valley after the LGM and into the Holocene. This combined glacial–periglacial chronological framework allows us to explore the timing of climatically controlled cryospheric response during the Holocene and their potential relationship with regional hydroclimatic variability. Our results contribute to a better understanding of cryosphere–climate interactions in mid-latitude mountain environments and provide new insights to test proposed hypothesis regarding glacial-periglacial transition at the end of the last ice age, as well as Holocene climate change in the subtropical southern latitudes.