Extensive early deglaciation and paleolake history of the Río Cisnes Ice Lobe, Patagonian Ice Sheet 44°S

GARCÍA, J.L.; MALDONADO, A.J.; DE PORRAS, M.E.; NUEVO DELAUNAY, A.; REYES, O.; EBENSPERGER, C.A.; BINNIE, S.A.; LÜTHGENS C.; MÉNDEZ, C.

QUATERNARY RESEARCH

ACADEMIC PRESS INC ELSEVIER SCIENCE

Lugar: Amsterdam; Año: 2018

0033-5894

The timing, structure and landscape change during the Patagonian Ice Sheet (PIS) deglaciation remains unresolved. In this paper, we provide a geomorphic, stratigraphic and geochronologic deglacial record of the Río Cisnes Glacier at 44°S and also from the nearby Río Ñirehuao and Río El Toqui Valleys (45°S) in the Chilean Patagonia. Our 14C, 10Be and OSL data indicate that after the Last Glacial Maximum, the Río Cisnes Glacier experienced c. 100 km deglaciation between >19.0 and 12.3 ka, accompanied by the formation of large glacial paleolakes. Deglaciation was interrupted by several ice readvances and by 16.9 ± 0.3 ka, Río Cisnes Glacier extended only c. 40% of its full glacial extent. The deglaciation of the Río Cisnes Glacier and other sensitive Patagonian glaciers occurred at least 1000 years earlier than the normally assumed start of local termination at c. 17.8 ka and coincided with West Antarctic isotope records. This early deglaciation can be linked to an orbital forced decline of Southern Ocean sea ice that embraced a distinct atmospheric warming trend, apparently recorded at least from West Antarctica through Patagonia.