Early deglaciation and paleolake history of Río Cisnes Glacier, Patagonian Ice Sheet (44°S)

Abstract

The timing, structure, and landscape change during the Patagonian Ice Sheet deglaciation remains unresolved. In this article, we provide a geomorphic, stratigraphic, and geochronological deglacial record of Río Cisnes Glacier at 44°S and also from the nearby Río Ñirehuao and Río El Toqui valleys (45°S) in Chilean Patagonia. Our 14C, 10Be, and optically stimulated luminescence data indicate that after the last glacial maximum, Río Cisnes Glacier experienced ~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 ~40% of its full glacial extent. The deglaciation of Río Cisnes Glacier and other sensitive Patagonian glaciers occurred at least 1 ka earlier than the ca. 17.8 ka normally assumed for the local termination, coincident with West Antarctic isotope records. This early deglaciation can be linked to an orbital forcing–driven decline of Southern Ocean sea ice associated with a distinct atmospheric warming that is apparent for West Antarctica through Patagonia.

The glacial geomorphology of the Río Corcovado, Río Huemul and Lago Palena/General Vintter valleys, northeastern Patagonia (43°S, 71°W)

“…However, with a few exceptions (e.g. García et al, 2019;Iglesias et al, 2016;Van Daele et al, 2016) there remains a general lack of published detailed mapping and geochronological data across the northeastern sector of the former ice sheet, between ∼39°S and ∼46.5°S (Darvill et al, 2015;Davies et al, 2020;Mendelová et al, 2017). Robust reconstructions from this region are needed to understand fully the PIS response to the Last Glacial Maximum (LGM) at these latitudes, and to investigate latitudinal dependencies on the timing of the local LGM throughout Patagonia (Darvill et al, 2015;Davies et al, 2020;García et al, 2018;Sagredo et al, 2011).…”

Multi‐millennial scale climate variability during MIS 3 and MIS 2 inferred from luminescence dating of coastal sand dunes and buried paleosol sequences in central Chile, 32°S

“…Overall dose rates were calculated based on the results from high‐resolution gamma spectrometry (Table ) and according to the conversion factors of Adamiec and Aitken (), and incorporating the effects of the cosmic dose rate (calculated with respect to geographical position, altitude and sediment overburden, according to Prescott and Hutton, ), as well as assuming an internal 40 K content for the potassium‐rich feldspar of 12.5 ± 0.5% (Huntley and Baril, ), and an a‐value of 0.08 ± 0.02 (García et al , ). An average water content of 10 ± 5% was included in the dose rate calculations.…”

“…As the measured residuals jointly and severally contribute less than $5% to the equivalent dose, and we observed good results from dose recovery tests without applying any correction for residuals (in agreement with previous studies summarized in Kars et al, 2014), we refrain from correcting for residuals. Overall dose rates were calculated based on the results from high-resolution gamma spectrometry (Table 2) and according to the conversion factors of Adamiec and Aitken (1998), and incorporating the effects of the cosmic dose rate (calculated with respect to geographical position, altitude and sediment overburden, according to Prescott and Hutton, 1994), as well as assuming an internal 40 K content for the potassium-rich feldspar of 12.5 AE 0.5% (Huntley and Baril, 1997), and an avalue of 0.08 AE 0.02 (García et al, 2019). An average water content of 10 AE 5% was included in the dose rate calculations.…”

Evidencias a cielo abierto para discutir superficies potenciales de actividad temprana en Patagonia centro occidental (44-45° s)

“…El retiro del hielo que ocupaba las cuencas de Cisnes y Ñirehuao durante el último máximo glacial (UMG) se caracterizó por la estabilización de varios frentes y la formación de lagos proglaciares de escala regional que se drenaron a través de pulsos, en un proceso que concluyó hace ca. 12.900 años atrás (García et al 2019). El incremento en humedad efectiva al oriente de la cordillera se inició hace 14.600 años llegando a su máximo hacia los 8.000 años cal AP como lo indica la información combinada del polen fósil de los testigos sedimentarios de El Shaman y El Embudo en el valle Cisnes (De Porras et al 2012, 2014.…”