Glaciar León, Chilean Patagonia: late-Holocene chronology and geomorphology

Abstract

Glaciar León is a temperate, grounded outlet of the eastern North Patagonian Icefield (NPI). It terminates at an active calving margin in Lago Leones, a 10 km long proglacial lake. We take a multidisciplinary approach to its description and use ASTER imagery and clast sedimentology to describe the geomorphology of the glacier and its associated moraines. We date periods of glacier retreat over the last 2500 years using a combination of lichenometric, dendrochronological, cosmogenic and optically stimulated luminescence techniques and show that the glacier receded from a large terminal moraine complex some 2500 years ago and underwent further significant recession from nineteenth-century moraine limits. The moraine dates indicate varying retreat rates, in conjunction with significant downwasting. The bathymetry of Lago Leones is characterized by distinct ridges interpreted as moraine ridges that dissect the lake into several basins, with water depths reaching 360 m. The fluctuations of Glaciar León appear to have been controlled by the interplay between climatic forcing and calving dynamics.

Holocene glaciations of Hielo Patag^|^oacute;nico (Patagonia Icefield), South America: A brief review

“…In the HPN, there are many damming moraines, which have not yet been studied, including at proglacial lakes of glaciares Fiero, Grosse, Steffen, Pared Norte, Piscis, Colonia, and Cachet. It is important to employ and combine many different dating techniques such as the one done by Harrison et al (2008) in areas such as the Hielo Patagónico where accessibility is very restricted under the year-around inclement weather conditions and sampling with a single technique is often severely limited.…”

“…Harrison et al (2007) reviewed LIA studies at eleven outlet glaciers (Reicher, Gualas, San Rafael, San Quintin, Arco, Colonia, Arenales-a branch of Colonia, Nef, Soler, León, Calafate, and Exploradores) of the HPN, concluding that glacier recession from maximal positions began in the early 1860s to the 1870s. Harrison et al (2008) used four complementary dating techniques, including cosmogenic isotopes, OSL, dendrochronology and lichenometry at Glaciar León of the HPN. They obtained a date of 2500 yr BP with OSL for a terminal moraine damming Lago Leones, and AD 1867 (LIA) with lichenometry for a moraine closest to the present glacier.…”

Holocene glacial variations in Central Patagonia, Aisen, Chile: geomorphological evidences.

“…2). Una edad levemente superior se atribuye a la morrena frontal que bloquea el lago Leones (46º30'S) situado en el margen oriental del Campo de Hielo Norte, donde Harrison et al (2008), utilizando isótopos cosmogénicos y dendrocronología, obtienen una edad media de 2.500 años cal. AP, es decir, más de 200 años que la morrena del valle del río Quetro (2.340 a 2.150 cal.…”

“…Solo se puede señalar que no se observaron cuñas de hielo, ni otros fenómenos de crioturbación que implicara la ocurrencia de climas fríos. Sin embargo, varios investigadores (Markgraf et al, 2007;Harrison et al, 2008;Moreno et al, 2009) proponen un incremento de la humedad acompañando la migración de los vientos del oeste hacia el norte, con consecuentes avances de los glaciares a escala milenial. Moreno et al (2009) han sistematizado la cronología de los múltiples avances comunicados para el Campo de Hielo Sur desde 6.000 años cal.…”

Precipitation as the main driver of Neoglacial fluctuations of Gualas glacier, Northern Patagonian Icefield

“…and Harrison, 1996;Harrison and Winchester, 1998;Harrison et al, 2007Harrison et al, , 2008. Reconstructions of earlier NPI glacier fluctuations are generally limited to a few radiocarbon ages obtained on organic deposits within or overlying frontal moraines (Heusser, 1960;Mardones et al, 2011).…”