Extensive mountain glaciation in central Patagonia during Marine Isotope Stage 5

Abstract

The timing and magnitude of glacial advances throughout a glacial cycle can give insight on the underlying drivers of climate change. Our knowledge of glacial activity early in a glacial cycle, however, is limited by incomplete preservation of the geomorphological record. Here, we present a 10 Be-dated glacial chronology from early in the last glacial cycle from the Belgrano valley, east of Monte San Lorenzo in central Patagonia. Our chronology reveals the

Glacier expansion in central Patagonia during the Antarctic Cold Reversal followed by retreat and stabilisation during the Younger Dryas

“…The two older moraine systems in the Belgrano valley ( Fig. 2) and associated chronologies are described by Mendelova et al (2019).…”

“…All Accelerator Mass Spectrometry (AMS) measurements were conducted at the Scottish Universities Environmental Research Centre (SUERC) AMS Facility. Sample prepa-ration for cosmogenic nuclide analysis is described in Mendelova et al (2019).…”

“…During full glacial conditions, the San Lorenzo ice cap coalesced with the larger PIS (Caldenius, 1932;Wenzens, 2005;Glasser et al, 2005;Mendelova et al, 2019). Ice from the San Lorenzo centre discharged northwards to join the Lago Puyerredón outlet glacier and south-eastwards into the Belgrano valley (Fig.…”

“…The Belgrano glacier reached its full last glacial extent at 75.0 ± 2.8 ka based on 10 Be exposure ages from outwash cobbles ( Fig. 2; Mendelova et al, 2019). This early maximum suggests that an independent ice mass developed on San Lorenzo early in the last glacial cycle toward the end of MIS 5.…”

“…A second major advance deposited the Menelik moraines dated using 10 Be ages at 24.7 ± 1.0 ka ( Fig. 2; Mendelova et al, 2019), coeval with the global Last Glacial Maximum (gLGM).…”