A composite 10Be, IR-50 and 14C chronology of the pre-Last Glacial Maximum (LGM) full ice extent of the western Patagonian Ice Sheet on the Isla de Chiloe, south Chile (42° S)

Unanswered questions about the glacier and climate history preceding the global Last Glacial Maximum (LGM) in the southern temperate latitudes remain. The Marine Isotope Stage (MIS) 3 is normally understood as a global interstadial period; nonetheless its climate was punctuated by conspicuous variability, and its signature has not been resolved beyond the polar realms. In this paper, we compile a Be-10 depth profile, single grain infrared (IR) stimulated luminescence dating and C-14 samples to derive a new glacier record for the principal outwash plain complex, deposited by the western Patagonian Ice Sheet (PIS) during the last glacial period (Llanquihue Glaciation) on the Isla de Chiloe, southern Chile (42 degrees S). In this region, the Golfo de Corcovado Ice Lobe left a distinct geomorphic and stratigraphic imprint, suitable for reconstructing former ice dynamics and timing of past climate change. Our data indicate that maximum glaciation occurred by 57.8 +/- 4.7 ka without reaching the Pacific Ocean coast. Ice readavanced and buttressed against the eastern side of the Cordillera de la Costa again by 26.0 +/- 2.9 ka. Our data further support the notion of a large ice extent during parts of the MIS 3 in Patagonia and New Zealand but appear to contradict near contemporaneous interstadial evidence in the southern midlatitudes, including Chiloe. We propose that the PIS expanded to its full-glacial Llanquihue moraines, recording a rapid response of southern mountain glaciers to the millennial-scale climate stadials that punctuated the MIS 3 at the poles and elsewhere.

Automated summary

This study compiles a new glacier record on Chiloe Island in southern Chile, revealing distinct expansions and retreats of glaciers during different periods, reflecting a rapid response to climate change during ice ages. The data support the presence of large glaciers in Patagonia and New Zealand during the MIS 3, but contradict evidence of interstadial periods in other mid-latitude regions.