Abstract
The late-glacial sedimentologic and geomorphic record of the former Patagonian ice sheet remains mostly unstudied despite the fact that it affords invaluable evidence for glaciologic processes during the last glacial-interglacial transition (i.e., 18-11.5 ka). This information is critical if landforms (e.g., moraines) and associated sediments are to be used for paleoclimate reconstruction. El Canal stratigraphic section in Torres del Paine, southern Chile (51ºS), provides one of the few complete late-glacial morphostratigraphic records preserved on land in Patagonia that has not been reworked by postglacial lake or marine transgressions. Therefore, it provides unique evidence for reconstructing former environments, processes and fluctuations along the ice front at the end of the last glaciation. Here, we present results of a morphostratigraphic study of this site, which was shaped during the late-glacial Torres del Paine-TDP II, III and IV glacier fluctuations. We document the presence of eight sediment lithofacies associations and six stratigraphic sections that expose a complete record of proximal to distal subaqueous processes, which we link to phases of glacier advance (e.g., moraine building) and retreat. During the late-glacial, the Lago del Toro ice lobe pushed and glaciotectonized ice-contact lake sediments several times to shape the TDP moraine ridges fringing present-day lake. The saw-toothed morphology of the ridges confirms the structural origin of these landforms. Based on sediment facies associations, we conclude that local glacial lakes developed along the ice front during deposition of the late-glacial TDP II-IV moraine belts, suggesting that collapse, and associated continental drainage diversion, of major regional-size lakes in Torres del Paine had occurred during this time.
Highlights
A complete record of late-glacial features and environments at the former Patagonian Ice Sheet margin, including sedimentologic and morphologic data within a precise chronological framework, is required to assess past ice-front dynamics and paleoclimate variability at the end of the last glaciation
El Canal stratigraphic section in Torres del Paine, southern Chile (51oS), provides one of the few complete late-glacial morphostratigraphic records preserved on land in Patagonia that has not been reworked by postglacial lake or marine transgressions
Based on sediment facies associations, we conclude that local glacial lakes developed along the ice front during deposition of the late-glacial TDP II-IV moraine belts, suggesting that collapse, and associated continental drainage diversion, of major regional-size lakes in Torres del Paine had occurred during this time
Summary
A complete record of late-glacial features and environments at the former Patagonian Ice Sheet margin, including sedimentologic and morphologic data within a precise chronological framework, is required to assess past ice-front dynamics and paleoclimate variability at the end of the last glaciation. We provide a detailed description of the late-glacial morphostratigraphic record of the former Lago del Toro ice lobe (Marden and Clapperton, 1995; García et al, 2014) in the Torres del Paine National Park surroundings, Chilean Patagonia (51oS; 73oW). About a hundred years ago, a two-kilometer long, west-east trench was artificially deepened at this location, within a natural glacial meltwater channel that cuts the Torres del Paine (TDP) I to IV end moraines deposited by the Lago del Toro ice lobe at the end of the last glaciation (Marden and Clapperton, 1995; García et al, 2012; García et al, 2014). Knowledge of the glacial processes linked to moraine construction is important, as these landforms are used to develop paleoclimate records (Marden and Clapperton, 1995; García et al, 2012)
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