Abstract
Understanding the timing of past glacial advances in Patagonia is of global climatic importance because of the insight this can provide into the influence on glacier behaviour of changes in temperature and precipitation related to the Southern Westerlies. In this paper we present new luminescence ages determined using single grains of K-feldspar from proglacial outwash sediments that were deposited by the Patagonian Ice Sheet around Lago Buenos Aires (∼46 °S), east of the contemporary Northern Patagonian Icefield. The new luminescence ages indicate that major outwash accumulations formed around ∼110 ± 20 ka to 140 ± 20 ka and that these correspond to the Moreno I and II moraine ridges, which were previously dated using cosmogenic isotope dating to 150 ± 30 ka. Luminescence dating at Lago Buenos Aires has also identified outwash sediments that were deposited during glacial advances ∼30.8 ± 5.7 ka and ∼34.0 ± 6.1 ka (MIS 3) that are not recorded in the moraine record. Younger outwash accumulations were then deposited between ∼14.7 ± 2.1 and 26.2 ± 1.6 ka which correspond to the Fenix I – V moraine ridges. The combined chronology suggests that glacial advances occurred ∼110 ± 20 ka to 150 ± 30 ka (MIS 6), ∼30.8 ± 5.7 ka to ∼34.0 ± 6.1 ka (MIS 3), and ∼14.7 ± 2.1 to 26.2 ± 1.6 ka (MIS 2) at Lago Buenos Aires. Overall luminescence dating using single grains of K-feldspar has excellent potential to contribute towards the ever-increasing geochronological dataset constraining the timings of glacial advances in Patagonia.
Highlights
Providing robust age constraints for the timing of past glacial advances can offer an important contribution to the global climate change debate
The single-grain ages determined for all of the samples in this study are shown in Fig. 7 in relation to the cosmogenic isotope ages provided for the moraine ridges (Kaplan et al, 2011) and the 40Ar/39Ar age provided for the Cerro Volcan lava flow (Singer et al, 2004)
The Fenix and Moreno samples can be clearly differentiated by the luminescence ages into different glacial periods, which is consistent with the pre-existing chronology
Summary
Providing robust age constraints for the timing of past glacial advances can offer an important contribution to the global climate change debate. Empirical datasets constraining climate change of the past can be used to test numerical models. Glasser et al, 2008) Providing accurate and precise age constraints on past glacial advances of the Patagonian Ice Sheet can be used to test the accuracy of ice-sheet models, and improve our understanding of how the Earth responds to long-term climatic change. Providing age constraints for glacial advances of the past can be challenging as some geochronological techniques are restricted by material availability and age ranges, but can be restricted by processes that have occurred since deposition. Researchers are beginning to incorporate these age sequences into Bayesian frameworks to model patterns of glacial advance and retreat (e.g. Chiverrell et al, 2013)
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
