Late-glacial fluctuations of two southern Patagonia outlet glaciers revealed by high-resolution seismic surveys

Abstract

Lago Argentino hosts various calving glaciers, among them the famous Perito Moreno. Whereas the onland late Pleistocene–Holocene glacial history is rather well constrained, the submerged glacier-related features were until now undisclosed. Here we present a series of high-resolution seismic profiles revealing moraine bodies associated with the late-glacial glacier dynamics and the first bathymetric map of the Brazo Rico and Brazo Sur, the two southern arms of Lago Argentino. At the eastern termination of Brazo Rico, we identified at the lake floor the submerged expression of the Puerto Bandera 3 moraine mapped onshore, which represents the oldest event (12,660 ± 70 cal yr BP oldest minimum age) recognized in this lake arm, and seven other younger events expressed by a series of terminal and recessional moraines. Along the Brazo Sur, few moraine bodies have been imaged by seismic data. Here, the youngest temporal constraint comes from the Frías moraine (ca. 6000 cal yr BP), which closes off the southern end of the Brazo Sur. At the confluence of the two arms, the Perito Moreno and the former Frías glacier merged and flowed toward east during their late-glacial maximum advance (i.e., Puerto Bandera 1 moraine). The subaqueous evidence of moraine bodies testifies to the occurrence of previously undocumented pulses of the Perito Moreno and former Frías glaciers within the general phase of late Pleistocene–Holocene regression.

The submerged footprint of Perito Moreno glacier

“…4C). Its internal reflector configurations resemble those characterizing the recessional moraines described by Lodolo et al 30 , and thus we interpret such a feature accordingly. The westernmost sector of Brazo Rico presents a more complex bathymetry than that of the southern sector of the Canal de Los Témpanos, and there are various morphological highs that reflect in many places the surrounding topography (Fig.…”

“…4, 5C, 5D). The overall internal architecture of this seismic facies is well-layered and made by sub-horizontal, sub-parallel, and continuous reflectors; it has been interpreted as a glacio-lacustrine deposit 30,31 .…”

“…Recently, Lodolo et al . 30 and Lozano et al . 31 , using bathymetric records and high-resolution seismic profiles, have unveiled the submerged glacial-related deposits along the two southern arms of Lago Argentino, i.e.…”

“…This is particularly true for the glaciers that now flow into Lago Argentino. Recently, Lodolo et al 30 and Lozano et al 31 , using bathymetric records and high-resolution seismic profiles, have unveiled the submerged glacialrelated deposits along the two southern arms of Lago Argentino, i.e. Brazo Rico ad Brazo Sur, some of which being correlated to those known onland.…”

“…1for locations) showing the expression of the subaqueous moraines identified at the lake-floor. Stratigraphic units indicated in the profiles are those described and individuated after Lodolo et al30 . https://doi.org/10.1038/s41598-020-73410-8…”