Gualas Glacier sedimentary record of climate and environmental change,Golfo Elefantes,Western Patagonia (46.5°S)

Abstract

Gualas Glacier is an outlet glacier of the Northern Patagonian Icefield, one of the largest temperate ice bodies on Earth. Golfo Elefantes, the depositional basin of Gualas Glacier, has a sedimentary record that spans, with some hiatuses, at least the last ~11.3±3.0 ka. During this period the gulf remained free of ice, as suggested by the absence of proximal glacimarine sediment and till in the sedimentary section. This implies that the arcuate terminal moraines that occur along the edges of Golfo Elefantes were formed during the waning stages of the local glacial maxima (Late Pleistocene) or the early Holocene. Between ~11.3±3.0 ka and ~4.2±0.3–1.4 ka, the basin received low sediment input consisting of fine-grained sediments in the form of low concentration density currents that filled bathymetric lows. Sediment discharge increased several times in the late Holocene (~<1.4 ka) and started with the accumulation of ~ 0.5 km³ of sandy sediments in a relatively short time span (~670 yr). This high discharge of sandy sediments is interpreted as being the result of glacial reworking of sediments stored in Gualas Glacier proglacial lake and thus implies that the glacier advanced at ~1.4–0.8 ka. The overall increase in sediment discharge in the late Holocene indicates a sharp increase in centennial timescale precipitation, which in turn suggests an increase in the intensity of the westerly winds in the area. Two recent periods of interannual sedimentation variability were identified at ~ad 1160–1460 and ~ad 1680–1890 and correlate with documented regional glacier advances.