The submerged footprint of Perito Moreno glacier

Abstract

Perito Moreno is the most famous calving glacier of the South Patagonia Icefield, the largest temperate glacier system of the Southern Hemisphere. Unlike most of the glaciers in the region that have strongly retreated in recent decades, the position of Perito Moreno glacier front remained relatively unchanged in the last century. However, earliest photographic documents show that, at the end of the nineteenth century, the front was ca. 800 m behind the current position. There is no reliable information about the positions of the Perito Moreno front in earlier times. Here we show evidence of two subaqueous moraine systems both in the Canal de Los Témpanos and in the Brazo Rico, the two arms of Lago Argentino along which Perito Moreno glacier has flowed over time. These moraines, identified for the first time in the Canal de Los Témpanos from bathymetric and high-resolution seismic profiles, mark the position of the largest glacier advance, tentatively correlated with the moraines of the “Herminita advance” identified and dated onland. We interpret these bedforms as the evidence of the most pronounced advance of Perito Moreno glacier during the mid-Holocene cooling event that characterized this sector of the Southern Hemisphere. This study highlights the importance of subaqueous glacial bedforms, representing decisive records of the glacial history and palaeoclimate, which could help unveiling the origin of the different behavior of glaciers like Perito Moreno that in a warming climate are relatively stable.

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

“…The acoustic basement of the Lago Roca Basin corresponds to the upper Cretaceous Cerro Toro Formation, as was also inferred for the acoustic basement of Brazo Rico and Brazo Sur (Lodolo, Donda, et al, 2020; Lodolo, Lozano, et al, 2020; Lozano et al, 2020). The stratified mudstones and sandstones of Cerro Toro Fm.…”

“…Deposits of the UU are thicker in the depressions of the basement top; they comprise a set of seismic facies (SF‐2 to SF‐5) most of which display similar patterns with layered, parallel reflections. Comparison with other seismic studies in Fuegian lakes (i.e., Lozano, Tassone, Bran, et al, 2018; Lozano, Tassone, Lodolo, et al, 2018; Waldmann et al, 2010; Waldmann, Ariztegui, Anselmetti, Coronato, & Austin Jr., 2010), or even in Brazo Rico and Brazo Sur (Lodolo, Donda, et al, 2020; Lodolo, Lozano, et al, 2020; Lozano et al, 2020) suggests that this configuration represents a glacio‐lacustrine sedimentation type. The lithology of the UU might be analogous to the three uppermost units of varves and rhythmites identified in the core sampled at Bahía Iveco (Del Valle et al, 1995).…”

“…Deposits of this type were interpreted by seismic signatures similar to submerged glacial deposits described in several Patagonian lakes (i.e., Bran et al, 2019; Lozano et al, 2018, 2018; Waldmann et al, 2008), and are typical in periglacial lakes. Particularly, these deposits were also recognized in the neighbouring Brazo Rico and Brazo Sur branches (Lodolo, Donda, et al, 2020; Lodolo, Lozano, et al, 2020; Lozano et al, 2020; Lozano, Bran, Lodolo, Tassone, & Vilas, 2021). Crested morphologies with several diffraction patterns of the reflections (Figure 3) can be interpreted as moraines, formed at the ice‐front during glacier advances or still‐stands.…”

“…In this work, we made a differentiation of the seismic record using the definition of seismic units, that is, parts of seismic sections with specific geometric patterns, stratigraphy, and architecture. Usually, the seismic units reflect particular sedimentation processes and conditions (i.e., Lodolo et al, 2020; Lodolo, Lozano, et al, 2020; Lozano et al, 2020). In addition, we have characterized each seismic unit into seismic facies.…”

Stratigraphic signature of the Perito Moreno ice-dammings during the Little Ice Age (southern Patagonia, Argentina)

“…The transparent red inset indicates the location of the study area. (b) The eastern Brazo Sur inlet where the three cores have been recovered; bathymetry is taken from Lodolo et al (2020a) and Lozano et al (2020).…”