Browsing by Author "Pérez Mora, Francia Débora"

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    10Be chronology of the Last Glacial Maximum and Termination in the Andes of central Chile: The record of the Universidad Glacier (34° S)
    (Elsevier Ltd., 2024) Fernández Navarro, Hans Andrés; García B., Juan Luis; Nussbaumer, Samuel U.; Tikhomirov, Dmitry; Pérez Mora, Francia Débora; Gartner Roer, Isabelle; Christl, Marcus; Egli, Markus
    Reconstructing mid-latitude glacier variations is a prerequisite for unveiling the interhemispheric climate linkages and atmospheric-ocean forcings that triggered those changes during the last glacial cycle. Nonetheless, the timing, magnitude, and structure of glacier fluctuations in the southern mid-latitudes remain incomplete. Here, we present a new Be-10 chronology of the Universidad Glacier in the Andes of central Chile (34 degrees S, 70 degrees W; similar to 2500 m a.s.l.) based on 21 cosmogenic-exposure ages of boulders on discrete moraine ridges defining former ice margins. Our findings include the mapping and dating of three moraines, UNI I, UNI II, and UNI III, located similar to 20 km, 15 km, and 10 km down-valley from the present-day glacier front, respectively. The Be-10 exposure ages of the UNI I moraine range from 135.9 +/- 7.1 to 51.4 +/- 2.7 ka (n = 3). The UNI II moraine gave a mean age of 18.0 +/- 0.9 (n = 15) and the UNI III moraine yielded a mean age of 13.9 +/- 0.8 ka (n = 3). The UNI I moraine implies the largest ice extent during a pre-Last Glacial Maximum (pre-LGM) period, including the penultimate glaciation. The UNI II is a moraine complex that represents cold and humid conditions in central Chile at the end of the LGM, which we attribute to the northward-shift of the Southern Westerly Winds (SWW). The UNI III moraine represents a return to glacial conditions interrupting the Termination, evidencing both a double-step deglacial trend observed through the southern middle and high latitudes at the end of the last ice age. The Andes at this subtropical latitude record a global signal of glacial and climate change.
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    Glacial to periglacial transition at the end of the last ice age in the subtropical semiarid Andes
    (Elsevier B.V., 2024) García B., Juan Luis; Carraha Molina, Javiera Paz; Fernández Navarro, Hans Andrés; Nussbaumer, Samuel U.; Pérez Mora, Francia Débora; Hidy, Alan J.; Gärtner-Roer, Isabelle; Haeberli, Wilfried
    Atmospheric warming and circulation reorganization at the end of the last ice age represent the most important climate change of the last 100,000 years and provide an opportunity to uncover how the southern subtropics cryosphere responded to strong changes in the global climate system. Extensive mapping and chronologic records on cryogenic landforms to better understand the association and interactions between glaciers and viscous creep of ice-rich permafrost landforms (rock glaciers) are widely missing in the region. In this paper, we reconstruct the geomorphic imprint of the Last Glacial Maximum (LGM) and the Termination I in the high Andes of the Río Limarí Basin (30–31°S) in the subtropical semiarid Andes of Chile. 74 new 10Be surface exposure dating ages constrain the timing of glaciation, deglaciation, and glacial to periglacial transition. Glacial advances occurred first by 41.2 ± 0.6 – 35.0 ± 0.5 ka during Marine Isotope Stage 3, but probably earlier also; then, a second advance occurred during the global LGM between 24.2 ± 0.4 and 18.6 ± 0.2 ka. Deglaciation by 17.6 ± 0.2 ka left extensive hummocky moraines on the main valleys. Characteristic patterns of furrows and ridges typical of rock glaciers and solifluction superimposed on the LGM hummocky moraine indicate ice-rich permafrost in glacial deposits likely between 15.5 ± 0.3 and 13.6 ± 0.3 ka. We propose that moraines deposited by LGM debris-covered glaciers served as a niche for strong seasonal frost and permafrost creep, which substantially modified the original landforms. Our results contribute to a better understanding of major transformations in an ice-rich high mountain area of the southern hemisphere where the interplay of temperature and precipitation changes drove glacial to periglacial transitions.