Description: Most outlet glaciers of the Cordillera Darwin Icefield (CDI; Patagonia, 54°S) are currently transitioning from calving to land-based conditions. Whether this situation is unique to the modern climate or also occurred during the Holocene is entirely unknown. Here, we investigate the Holocene fluctuations of outlet glaciers from the northern flank of the CDI using a multi-proxy sedimentological and geochemical analysis of a 13.5 m long sediment core from Almirantazgo fjord. Our results demonstrate that sedimentation in Almirantazgo fjord started prior to 14,300 cal yr BP, with glacier-proximal deposits occurring until 13,500 cal yr BP. After 12,300 cal yr BP, most glaciers had retreated to land-locked locations and by 9800 cal yr BP, Almirantazgo fjord was a predominantly marine fjord environment with oceanographic conditions resembling the present-day setting. Our sediment record shows that during the first part of the Holocene, CDI glaciers were almost entirely land-based, with a possible re-advance at 7300-5700 cal yr BP. This is in clear contrast with the Neoglaciation, during which CDI glaciers rapidly re-advanced and shrank back several times, mostly in phase with the eastern outlet glaciers of the Southern Patagonian Icefield (SPI). Two significant meltwater events, indicative of rapid glacier retreat, were identified at 3250-2700 and 2000-1200 cal yr BP, based on an increase in grain-size mode and related inorganic geochemical parameters. This interpretation is additionally supported by concomitant decreases in organic carbon of marine origin and in Cl counts (salinity), reflecting higher terrestrial input to the fjord and freshening of the fjord waters. Overall, our record suggests that CDI outlet glaciers advanced in phase with eastern SPI glaciers during the Neoglaciation, and retreated far enough into their valleys twice to form large outwash plains. Our results also highlight the potential of fjord sediments to reconstruct glacier variability at high resolution on multi-millennial timescales.

Description: We performed geochemical and sedimentological analyses on a 12.2 m long, radiocarbon-dated sediment core collected from Wide Channel (50°S; Chile) to reconstruct fluctuations of the marine-terminating HPS19, Penguin and Europa glaciers, located along the western side of the Southern Patagonian Icefield. The JPC42 sediment core was collected with a Jumbo Piston corer onboard the RV/IB Nathaniel B. Palmer in July 2005. An additional 1.5 m long Kasten core (KC41) was retrieved to sample the sediment-water interface. Both cores were scanned on an ITRAX XRF core scanner at WHOI in August 2008 and then sampled in 2 cm thick slices (ca.10 cm³) every 10 cm at the Marine and Geology Repository of Oregon State University in February 2021. Samples were freeze-dried at Ghent University, and all discrete analyses were performed at a 10 cm interval, except for CaCO3 in the lower 5.9 m of the core, which was analyzed at a 20 cm interval.

Description: Organic geochemical and sedimentological data analyzed at a 10 to 20 cm interval on the JPC42 and KC41 cores including total organic carbon content, stable carbon isotopes, marine organic carbon content, calcium carbonate, grain-size mode, and ice-rafted debris (particles 〉150 µm).