Browsing by Author "Martini, Mateo A."

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    Glacier fluctuations in the northern Patagonian Andes (44°S) imply wind-modulated interhemispheric in-phase climate shifts during Termination 1
    (2022) Soteres García, Rodrigo León; Sagredo T., Esteban; Kaplan, Michael R.; Martini, Mateo A.; Moreno, Patricio I.; Reynhout, Scott A.; Schwartz, Roseanne; Schaefer, Joerg M.Soteres García, Rodrigo León; Sagredo T., Esteban; Kaplan, Michael R.; Martini, Mateo A.; Moreno, Patricio I.; Reynhout, Scott A.; Schwartz, Roseanne; Schaefer, Joerg M.
    The Last Glacial Termination (T1) featured major changes in global circulation systems that led to a shift from glacial to interglacial climate. While polar ice cores attest to an antiphased thermal pattern at millennial timescales, recent well-dated moraine records from both hemispheres suggest in-phase fluctuations in glaciers through T1, which is inconsistent with the bipolar see-saw paradigm. Here, we present a glacier chronology based on 30 new 10Be surface exposure ages from well-preserved moraines in the Lago Palena/General Vintter basin in northern Patagonia (~ 44°S). We find that the main glacier lobe underwent profound retreat after 19.7 ± 0.7 ka. This recessional trend led to the individualization of the Cerro Riñón glacier by ~ 16.3 ka, which underwent minor readvances at 15.9 ± 0.5 ka during Heinrich Stadial 1, during the Antarctic Cold Reversal with successive maxima at 13.5 ± 0.4, 13.1 ± 0.4, and 13.1 ± 0.5 ka, and a minor culmination at 12.5 ± 0.4 ka during Younger Dryas time. We conclude that fluctuations of Patagonian glaciers during T1 were controlled primarily by climate anomalies brought by shifts in the Southern Westerly Winds (SWW) locus. We posit that the global covariation of mountain glaciers during T1 was linked to variations in atmospheric CO2 (atmCO2) promoted by the interplay of the SWW-Southern Ocean system at millennial timescales.
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    The glaciovolcanic evolution of the Copahue volcano, Andean Southern Volcanic Zone, Argentina-Chile
    (2020) Baez, Alejandro D.; Baez, Walter; Caselli, Alberto T.; Martini, Mateo A.; Sommer, Carlos A.
    Glaciovolcanism produces distinctive features that are useful paleoclimate proxies for the distribution of past ice sheets and glacier extent. The Copahue volcano located in the Andean Southern Volcanic Zone. Argentina-Chile, is an active composite volcano known to have glaciovolcanic features such as lava bodies with glassy margins and anomalous cooling fractures. However, the emplacement conditions of these products and the influence of Pleistocene glaciations on the evolution of the Copahue volcano remains poorly understood. In this contribution, we propose a model for glaciovolcanic evolution of the Copahue volcano based on the analysis, interpretation, and mapping of its products. Ten lithofacies are described on the eastern flank of Copahue volcano exhibiting several examples of glaciovolcanism. The evolution of the Copahue volcano can be divided into two main sequences: the Ancient Sequence (S1) and the Young Sequence (S2), separated by a major erosive phase. The S1 (early-middle Pleistocene-late Pleistocene) consists of an initial subaerial effusive stage followed by a major glaciovolcanic stage, during which a thick ice cap existed and the edifice grew beneath an englacial lake with the eventual formation of a lava-fed delta. The S2 (late Pleistocene-Present) is defined by mainly effusive activity during periods of glacial advance and retreat recorded by an alternation of unconfined subaerial lavas and ice-confined lavas. The evolution of the Copahue volcano therefore indicates two glaciations in the Copahue-Caviahue area during the late Pleistocene, in contrast to a single glaciation. Based on the glacial history in the area we associate the first glaciation with the end of Marine Isotope Stage 3 (57-29 ka) and/or the Last Glacial Maximum period (26.5-19.0 ka), and the second less-extensive glacial period with the Antarctic Cold Reversal (14.5-12.9 ka). (C) 2020 Elsevier B.V. All rights reserved.