Late Glacial and Holocene glacier fluctuations at Nevado Huaguruncho in the Eastern Cordillera of the Peruvian Andes

Abstract

Discerning the timing and pattern of late Quaternary glacier variability in the tropical Andes is important for our understanding of global climate change. Terrestrial cosmogenic nuclide (TCN) ages (48) on moraines and radiocarbon-dated clastic sediment records from a moraine-dammed lake at Nevado Huaguruncho, Peru, document the waxing and waning of alpine glaciers in the Eastern Cordillera during the past ~15 k.y. The integrated moraine and lake records indicate that ice advanced at 14.1 ± 0.4 ka, during the first half of the Antarctic Cold Reversal, and began retreating by 13.7 ± 0.4 ka. Ice retreated and paraglacial sedimentation declined until ca. 12 ka, when proxy indicators of glacigenic sediment increased sharply, heralding an ice advance that culminated in multiple moraine positions from 11.6 ± 0.2 ka to 10.3 ± 0.2 ka. Proxy indicators of glacigenic sediment input suggest oscillating ice extents from ca. 10 to 4 ka, and somewhat more extensive ice cover from 4 to 2 ka, followed by ice retreat. The lack of TCN ages from these intervals suggests that glaciers were less extensive than during the late Holocene. A final Holocene advance occurred during the Little Ice Age (LIA, ca. 0.4 to 0.2 ka) under colder and wetter conditions as documented in regional proxy archives. The pattern of glacier variability at Huaguruncho during the Late Glacial and Holocene is similar to the pattern of tropical Atlantic sea-surface temperatures, and provides evidence that prior to the LIA, ice extent in the eastern tropical Andes was decoupled from temperatures in the high-latitude North Atlantic.

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

“…For the reasons outlined in Section 3.1, many studies take the oldest boulder age-within a cluster of boulder ages for a given moraine and after the exclusion of outliers attributed to nuclide inheritance-to be the closest to the timing of the glacier advance (e.g., Zech et al, 2006Zech et al, , 2007aZech et al, ,b, 2009bZech et al, , 2010Hall et al, 2009;May et al, 2011). On the contrary, some studies instead (i) calculate mean values of all boulder ages collected on a moraine (Licciardi et al, 2009;Shakun et al, 2015b;Stansell et al, 2015Stansell et al, , 2017Bromley et al, 2016;Martini et al, 2017); (ii) calculate average boulder ages using frequency density plots (Smith and Rodbell, 2010;Jomelli et al, 2011;Smith et al, 2011;Ward et al, 2015); (iii) organise ages chronologically and take the plateau or modal age (Smith et al, 2005a,b) or (iv) combine these various approaches . As our results for the Sierra de Aconquija demonstrate (see Section 4.1), these different approaches could, in some cases, result in substantially different moraine ages (and consequently palaeoclimate interpretations) for an identical set of boulder ages.…”

The last deglaciation of Peru and Bolivia

“…Newly published data from the Cordillera Carabaya (Bromley et al, 2016) and Nevado Huaguruncho (Stansell et al, 2015) were calculated by the authors using the Quelccaya production rates. We also use radiocarbon ages in the compilation by Rodbell et al (2009), combined with more recent publications for the Cordillera Huayhuash , Cordillera Raura (Stansell et al, 2013), and Nevado Huaguruncho (Stansell et al, 2015) (Table 2). LGM (>42 ka); currently small glaciers remain on Cerro Chuchpanga to west of Junin.…”

“…In the case of Illimani (Smith et al, 2011), ages were not available in the Shakun et al (2015a) composite, and we recalculated with the Quelccaya 10 Be production rate calibration (Kelly et al, 2015), and the CRONUS-Earth calculator version 2.3 with the time-invariant 'St' scaling method of Stone (2000) following Lal (1991). Newly published data from the Cordillera Carabaya (Bromley et al, 2016) and Nevado Huaguruncho (Stansell et al, 2015) were calculated by the authors using the Quelccaya production rates. We also use radiocarbon ages in the compilation by Rodbell et al (2009), combined with more recent publications for the Cordillera Huayhuash , Cordillera Raura (Stansell et al, 2013), and Nevado Huaguruncho (Stansell et al, 2015) (Table 2).…”

“…The features dated by Stansell et al (2015) are contained within a broad cirque with lakes at ~4300 m that captures glaciers with southerly and easterly aspect. The moraine mapped as bounding Yanacocha is parallel with other laterals that exit to the east and south, terminating ~4000 m. These are likely late-glacial in age, but do not extend to the limits of the longer glacial valleys of U-shape form, indicating earlier extensions of ice were larger.…”

“…Lake sediments and TCN exposure ages provide a detailed integrated record of the timing of Late Glacial and Holocene glacial activity at Nevado Huaguruncho in the Eastern Cordillera of the tropical Peruvian Andes (Stansell et al, 2015). Glaciers expanded ca.…”