Browsing by Author "Moreno, Patricio I."
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- ItemEnvironmental evolution of western Tierra del Fuego (∼54°S) since ice-free conditions and its zonal/hemispheric implications(2023) Moreno, Patricio I.; Lambert, Fabrice; Hernández, Loreto; Villa Martínez, Rodrigo P.By virtue of its position adjacent to the Drake Passage, Tierra del Fuego in South America allows examining the vegetation and environmental history of the southernmost continental landmass outside Antarctica, and the evolution of the Southern Westerly Winds-Southern Ocean (SWW–SO) coupled system since the Last Glacial Maximum (LGM). For that purpose, we studied sediment cores from Lago Charquito, a small closed-basin lake in central-west Tierra del Fuego with a continuous lacustrine record since ~17.3 ka. Ice-free conditions at the site imply a ~70 km retreat of the Bahía Inútil glacier lobe from its LGM position during a ~800-year interval, a trend that continued until its disappearance ~100 km upstream from L. Charquito, ~800 years later. Our palynological data show an open landscape dominated by cold-tolerant shrubs and herbs between ~17.3–12.9 ka, with increases in precipitation of SWW origin at ~16.3 ka, ~14.7 ka, between ~8.7–7.6 ka, and after ~6.8 ka. Warming at ~12.9 ka initiated an abrupt afforestation trend that stalled during the early Holocene (~12–8.7 ka) owing to a precipitation decline and wildfires, and later resumed in response to invigorated SWW. We hypothesize that sparse Nothofagus tree populations inhabited the periphery of the Patagonian Ice Sheet (PIS) during the LGM and migrated toward the Andes contemporaneous with glacier recession as temperature rose during the Last Glacial Termination (T1). We posit that besides establishing topographic and climatic barriers for land biota, the PIS enabled the connectivity of cold-tolerant hygrophilous plant populations along a humid fringe adjacent to its land-based perimeter, despite the presumably dry conditions downwind from the eastern PIS margin. Our results suggest that southward shifts or expansion of the SWW toward or beyond Tierra del Fuego enhanced upwelling and ventilation of deep waters in the SO, northward shifts or weakening had the opposite effect. We observe that the time evolution of atmospheric CO2 concentrations, high-latitude air and sea-surface temperatures, and sea level during T1 fall short in explaining the timing and abruptness of the Bahía Inútil glacier lobe collapse, and quite possibly multiple other glacier lobes from the PIS.
- ItemGlacier 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.
- ItemHolocene tephrochronology around Cochrane (~47° S), southern Chile(2016) Stern, Charles R.; Moreno, Patricio I.; Henriquez, William I.; Villa Martinez, Rodrigo; Sagredo T., Esteban; Aravena, Juan Carlos; De Pol-Holz, Ricardo
- ItemRefinement of the tephrostratigraphy straddling the northern Patagonian Andes (40–41°S): new tephra markers, reconciling different archives and ascertaining the timing of piedmont deglaciation(2022) Alloway, Brent V.; Pearce, Nicholas J.G.; Moreno, Patricio I.; Villarrosa, Gustavo; Jara, Ignacio A.; Henríquez, Carla A.; Sagredo T., Esteban; Ryan, Matthew T.; Outes, ValeriaWe describe the stratigraphy, age, geochemistry and correlation of tephra from west to east across the northern Patagonian Andes (c. 40–41°S) with a view to further refining the eruptive history of this region back to the onset of the Last Glacial Termination (~18 cal. ka). Eastwards across the Andes, rhyodacite to rhyolitic tephra markers of dominantly Puyehue-Cordón Caulle source are persistently recognised and provide a stratigraphic context for more numerously erupted intervening tephra of basalt to basaltic–andesite composition. Tephra from distal eruptive centres are also recognised. West of the Andean Cordillera, organic-rich cores from a small closed lake basin (Lago Pichilafquén) reveal an exceptional high-resolution record of lowland vegetation–climate change and eruptive activity spanning the last 15 400 years. Three new rhyodacite tephra (BT6-T1, -T2 and -T4) identified near the base of the Pichilafquén record, spanning 13.2 to 13.9 cal. ka bp, can be geochemically matched with correlatives in basal andic soil sequences closely overlying regolith and/or basement rock. The repetitiveness of this tephrostratigraphy across this Andean transect suggests near-synchronous tephra accretion and onset of up-building soil formation under more stable (revegetating) ground-surface conditions following rapid piedmont deglaciation on both sides of the Cordillera by at least ~14 cal. ka bp.
- ItemStratigraphy, age and correlation of Lepué Tephra: a widespread c. 11 000 cal a BP marker horizon sourced from the Chaitén Sector of southern Chile(2017) Brent V. Alloway; Moreno, Patricio I.; Pearce, Nick J. G.; De Pol Holz, Ricardo; Henríquez, William I.; Pesce, Oscar H.; Sagredo T., Esteban; Villarosa, Gustavo; Outes, Valeria
- ItemTrans-pacific glacial response to the Antarctic Cold Reversal in the southern mid-latitudes(2018) Sagredo T., Esteban; Kaplan, Michael R.; Araya, Paola S.; Lowell, Thomas V.; Aravena, Juan C.; Moreno, Patricio I.; Kelly, Meredith A.; Schaefer, Joerg M.