Browsing by Author "Binnie, Steven A."

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    A composite 10Be, IR-50 and 14C chronology of the pre-Last Glacial Maximum (LGM) full ice extent of the western Patagonian Ice Sheet on the Isla de Chiloe, south Chile (42° S)
    (2021) Garcia, Juan-Luis; Luthgens, Christopher; Vega, Rodrigo M.; Rodes, Angel; Hein, Andrew S.; Binnie, Steven A.
    Unanswered questions about the glacier and climate history preceding the global Last Glacial Maximum (LGM) in the southern temperate latitudes remain. The Marine Isotope Stage (MIS) 3 is normally understood as a global interstadial period; nonetheless its climate was punctuated by conspicuous variability, and its signature has not been resolved beyond the polar realms. In this paper, we compile a Be-10 depth profile, single grain infrared (IR) stimulated luminescence dating and C-14 samples to derive a new glacier record for the principal outwash plain complex, deposited by the western Patagonian Ice Sheet (PIS) during the last glacial period (Llanquihue Glaciation) on the Isla de Chiloe, southern Chile (42 degrees S). In this region, the Golfo de Corcovado Ice Lobe left a distinct geomorphic and stratigraphic imprint, suitable for reconstructing former ice dynamics and timing of past climate change. Our data indicate that maximum glaciation occurred by 57.8 +/- 4.7 ka without reaching the Pacific Ocean coast. Ice readavanced and buttressed against the eastern side of the Cordillera de la Costa again by 26.0 +/- 2.9 ka. Our data further support the notion of a large ice extent during parts of the MIS 3 in Patagonia and New Zealand but appear to contradict near contemporaneous interstadial evidence in the southern midlatitudes, including Chiloe. We propose that the PIS expanded to its full-glacial Llanquihue moraines, recording a rapid response of southern mountain glaciers to the millennial-scale climate stadials that punctuated the MIS 3 at the poles and elsewhere.
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    Early deglaciation and paleolake history of Río Cisnes Glacier, Patagonian Ice Sheet (44°S)
    (2019) García B., Juan Luis; Maldonado, Antonio; De Porras, María Eugenia; Nuevo Delaunay, Amalia; Reyes, Omar; Ebensperger, Claudia; Binnie, Steven A.; Lüthgens, Christopher; Méndez, César
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    The Last Glacial Maximum and Deglacial History of the Seno Skyring Ice Lobe (52°S), Southern Patagonia
    (2022) Lira, Maria-Paz; Garcia, Juan-Luis; Bentley, Michael J.; Jamieson, Stewart S. R.; Darvill, Christopher M.; Hein, Andrew S.; Fernandez, Hans; Rodes, Angel; Fabel, Derek; Smedley, Rachel K.; Binnie, Steven A.
    There are still many uncertainties about the climatic forcing that drove the glacier fluctuations of the Patagonian Ice Sheet (PIS, 38-55 degrees S) during the last glacial period. A key source of uncertainty is the asynchrony of ice lobe fluctuations between the northern, central, and southern PIS. To fully understand the regional trends requires careful mapping and extensive geochronological studies. This paper presents geomorphological and geochronological reconstructions of the glacial and deglacial landforms formed during the last glacial period at the Seno Skyring lobe, southernmost Patagonia (52 degrees S, 71 degrees W). We present a detailed geomorphological map, where we identify two moraine systems. The outer and older is named Laguna Blanca (LB) and the inner Rio Verde (RV). The LB moraines were built subaerially, whereas parts of the RV were deposited subaqueously under the palaeo lake Laguna Blanca, which developed during deglaciation. We conducted surface exposure Be-10 dating methods on boulder samples collected from LB and RV glacial margins. The moraine LB III and LB IV formed at 26.3 +/- 2.3 ka (n = 5) and 24.3 +/- 0.9 ka (n = 3), respectively. For the inner RV moraine, we obtained an age of 18.7 +/- 1.5 ka (n = 6). For the palaeo Laguna Blanca evolution, we performed Be-10 exposure ages on shoreline berms and optically stimulated luminesce dating to constrain the lake levels, and Be-10 depth profile dating on an outwash deposit formed by a partial lake drainage event, which occurred at 22 +/- 3 ka. For the RV moraine deglaciation, we performed radiocarbon dating of basal sediments in a peat bog, which indicates that the glacier retreated from the terminal RV moraine by at least c. 16.4 cal kyr BP. Our moraine geochronology shows an asynchrony in the maximum extents and a different pattern of ice advances between neighbouring lobes in southern Patagonia. We speculate that this may be due, at least in part, to the interaction between topography and the precipitation carried by the southern westerly wind belt. However, we found broad synchrony of glacial readvances contemporaneous with the RV moraine.
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    The MIS 3 maximum of the Torres del Paine and Última Esperanza ice lobes in Patagonia and the pacing of southern mountain glaciation
    (2018) García B., Juan Luis; Hein, Andrew S.; Binnie, Steven A.; Gómez, Gabriel A.; González, Mauricio A.; Dunai, Tibor J.