First cosmogenic ages for glacial deposits from the Plata range (33° S): New inferences for Quaternary landscape evolution in the Central Andes

In the region of the Stepanek rock glacier (69 19 0 /69 26 0 W, 32 55 0 /32 59 0 S), in the Province of Mendoza, Argentina, seasonal hydrochemical monitoring was carried out between 2013 and 2017. This paper describes underground and surface water flow, and their hydrochemistry, and provides an overview of how groundwater interacts with the rock glacier. The cryogenic basin of the study area where the hydrological flows originate has a surface area of 11.5 km 2 . The Stepanek rock glacier fills the valley and its permafrost influences water flow. Isotopic analyses of surface ephemeral streams and groundwater were made. Characteristic, naturally occurring δ 2 H and δ 18 O signatures of these samples indicate strongly that they are fed from within permafrost from the rock glacier, in response to the degradation of permafrost and melting of ground ice. Elevated values of Ni 2+ , Cd 2+ and Zn 2+ were detected in the meltwater runoff. Due to lithological factors, the Andean periglacial environment may indicate altitudinal differences in the hydrogeochemical results. Our hydrogeochemical research allows the interpretation of different water flows, directly observed or indirectly deduced, which cross the rock glacier. The new information allows for the development of a new conceptual rock glacier model that includes different flow paths. It is expected that this will become more important due to ongoing climate change.

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“…The major part of the Stepanek rock glacier (Figures and ) is considered by Moreiras et al . as a debris‐covered glacier.…”

Section: Discussionmentioning

confidence: 99%

“…To define ages of the moraines and the cryosphere system, Moreiras et al . have used cosmogenic dating.…”

Section: Study Areamentioning

confidence: 99%

Periglacial water paths within a rock glacier‐dominated catchment in the Stepanek area, Central Andes, Mendoza, Argentina

Liaudat

Sileo

Dapeña

2020

Permafrost & Periglacial

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“…Zech et al (2008) argues for a ~40 ka advance based on a review of records in Patagonia and south-central Chile. Recent cosmogenic glacial records both from the tropics (e.g., Bromley et al, 2016) and subtropical Argentina (e.g., Moreiras et al, 2016) indicate moraine formation at ca. 40 ka and 25 ka.…”

Section: Discussionmentioning

confidence: 99%

Across the Arid Diagonal: deglaciation of the western Andean Cordillera in southwest Bolivia and northern Chile

Ward

Thornton

Cesta

2017

CIG

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“…4). All sites with dated moraines south of the Sierra de Aconquija (e.g., Zech et al, 2006;2007a;Moreiras et al, 2017;Terrizzano et al, 2017) are situated on the western flank of the Andes, where moisture is sourced from the Pacific westerlies. While it would be worthwhile to review how fluctuations in the Pacific westerlies influenced glaciers in the Southern Andes, this consideration lies beyond the scope of the present study.…”

Section: Andesmentioning

confidence: 99%

Timing of past glaciation at the Sierra de Aconquija, northwestern Argentina, and throughout the Central Andes

D’Arcy

Schildgen

Strecker

et al. 2019

Quaternary Science Reviews

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Advances in cosmogenic nuclide exposure dating have made moraines valuable terrestrial recorders of palaeoclimate. A growing number of moraine chronologies reported from the Central Andes show that tropical glaciers responded sensitively to past changes in precipitation and temperature over timescales ranging from 10 3 to 10 5 years. However, the causes of past glaciation in the Central Andes remain uncertain. Explanations have invoked insolation-modulated variability in the strength of the South American Summer Monsoon, teleconnections with the North Atlantic Ocean, and/or cooling in the Southern Hemisphere.The driver for these past climate changes is difficult to identify, partly due to a lack of dated moraine records, especially in climatically sensitive areas of the southern Central Andes.Moreover, new constraints are needed on precisely where and when glaciers advanced. We use cosmogenic 10 Be produced in situ to determine exposure ages for three generations of moraines at the Sierra de Aconquija, situated at 27°S on the eastern flank of the southern Central Andes. These moraines record glacier advances at approximately 22 ka and 40 ka, coincident with summer insolation maxima in the sub-tropics of the Southern Hemisphere, as well as at 12.5 ka and 13.5 ka during the Younger Dryas and the Antarctic Cold Reversal, respectively. We also identify minor glaciation during Bond Event 5, also known as the 8.2 ka event. These moraines register past climate changes with high fidelity, and currently constitute the southernmost dated record of glaciation on the eastern flank of the Central Andes. To contextualise these results, we compile 10 Be data reported from 144 moraines in the eastern Central Andes that represent past glacier advances. We re-calculate exposure ages from these data using an updated reference production rate, and we re-interpret the moraine ages by taking the oldest clustered boulder age (after the exclusion of outliers attributed to nuclide inheritance) as closest to the timing of glacier advance-an approach for which we provide empirical justification. This compilation reveals that Central Andean glaciers have responded to changes in temperature and precipitation. We identify cross-latitude advances in phase with insolation cycles, the last global glacial maximum, and episodes of strengthened monsoonal moisture transport including the Younger Dryas and Heinrich Stadials 1 and 2. Our results from the Sierra de Aconquija allow us to constrain the southerly limit of enhanced precipitation associated with Heinrich Stadials at ~25°S. More broadly, our findings demonstrate at both local and regional scales that moraines record past climate variability with a fine spatial and temporal resolution.3

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First cosmogenic ages for glacial deposits from the Plata range (33° S): New inferences for Quaternary landscape evolution in the Central Andes

Cited by 16 publications

References 70 publications

Periglacial water paths within a rock glacier‐dominated catchment in the Stepanek area, Central Andes, Mendoza, Argentina

Periglacial water paths within a rock glacier‐dominated catchment in the Stepanek area, Central Andes, Mendoza, Argentina

Across the Arid Diagonal: deglaciation of the western Andean Cordillera in southwest Bolivia and northern Chile

Timing of past glaciation at the Sierra de Aconquija, northwestern Argentina, and throughout the Central Andes

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