‘Palaeolago Fueguino’, a Late Pleistocene lacustrine basin located in the central sector of Tierra del Fuego: a seismostratigraphic study

Abstract

At~20 ka BP, lakes Yehuin, Chepelmut and Fagnano constituted a single, large water body in the central part of Isla Grande de Tierra del Fuego (southernmost Patagonia). The evolutionary history of this lake, known as 'Palaeolago Fueguino', was probably controlled by the advances, stillstands and retreats of the 'Fagnano Palaeoglacier', an outlet glacier that flowed eastward from the Darwin Cordillera ice sheet. A detailed analysis of high-resolution seismic reflection profiles acquired within the three lakes has allowed the identification and correlation of seven unconformities within the lacustrine sedimentary infill, three seismostratigraphic sequences in Lago Fagnano and four in Lago Yehuin. A seismic stratigraphic correlation between these sequences suggests that these basins formerly constituted a single, large lacustrine body. A lake-level curve of the evolutionary stages of each lake, derived from the seismostratigraphic analysis of the sedimentary infill is proposed here, representing a 17.5 ka-long record. It was further integrated with the glacial record of the advances and retreats of the Fagnano Palaeoglacier. This study has implications for interpreting the sedimentary history of lake basins in glaciated mountain ranges.

Structure, seismostratigraphy, and tectonic evolution of Lago Roca (southern Patagonia, Argentina)

“…Assuming a maximum age for the onset of the lacustrine sedimentation of ~12.6 kyr B.P., and an average sound velocity of 1,650 m/s for the time‐to‐depth conversion for the UU (based on the seismic analysis of Lozano et al, 2020), the sedimentation rate can be estimated as 6.5 mm/yr in the deepest sectors of the basin, and a mean of 4.6 mm/yr. These values are higher than the ones reported for the glacio‐lacustrine units of some Fuegian lakes, Yehuin (1.4 mm/yr), Chepelmut (2.4 mm/yr) and Fagnano (3.8 mm/yr in the Rio Claro river mouth; Lozano et al, 2021). The main source of sediment input into the lake system and the high sedimentation rates are possibly related to the proximity of the glaciers in the southern arms of Lago Argentino during the last 10 kyr, and the different nature of the Lago Argentino glacial system, related to the Southern Patagonian Icefield.…”

Horizontal and Vertical Deformation Rates Linked to the Magallanes‐Fagnano Fault, Tierra Del Fuego: Reconciling Geological and Geodetic Observations by Modeling the Current Seismic Cycle

“…The fault section sampled by our near‐fault GNSS sites corresponds to a large extent with the valley occupied by Lake Fagnano and almost all prominent positive residuals concentrate within this area. During the Last Glacial Maximum (LGM, ∼20 ka ago) this valley was completely occupied by an ice lobe (e.g., Lozano et al., 2021; Rabassa et al., 2011; Waldmann, Ariztegui, et al., 2010). This lobe formed part of the extensive glacial system that extended from the Cordillera Darwin into the valleys today occupied by the Beagle Channel and the branches of the Strait of Magellan (e.g., McCulloch et al., 2005).…”