Evolution of sediment-landform assemblages at a recently deglaciated terrain: The case of the Grey glacier in southern Patagonia

SOTERES, RODRIGO L.; GUERRA, LUCIA; CARRASCO, R; RADA, C; CIFUENTES, P; RUBIO, A; RIQUELME, FABIAN; MATEO MARTINI; SAGREDO, ESTEBAN; HAVIA, R; KAPLAN, M.R.; PEDRAZA, J; ARAVENA, JUAN CARLOS; SANCHEZ-BARACLADO, P

Roma

Congreso; XXI INQUA Congress; 2023

Patagonian glaciers have been retreatingrapidly during the past decades leaving behind a suite of sediment-landformassemblages that reflect the response of the cryosphere to severe warmingepisodes in addition to non-climatic factors, such as topography and/or theexistence of proglacial lakes. Combining remote sensing techniques,geomorphological mapping, lithological descriptions, sedimentary analysis andSchmidt hammer measurements, we assess glacier-landscape dynamics, includingdebris transport paths, deposition environments characteristics and weatheringrates of the Grey glacier in southern Patagonia (~51o S). Our aim isto outline a detailed morphosedimentary model for a temperate glacier tofurther understand processes involved in glacier withdrawal and to provide amodern analog to improve paleoclimate reconstructions based on glacial geology.Our preliminary results indicate that the ice receded ~1.6 km from theinnermost moraine to its present-day position since at least 1974. We identifya suite of sedimentary-landforms assemblages which indicate that the glacierterminus transitioned from terrestrial to lacustrine environments in pastdecades, such as subaerial and subaqueous moraines, shorelines and terraces. Wehypothesized that dominant lithofacies varies from angular-to-subangularbouldery gravel tills in ice marginal features to angular gravels insupraglacial deposits and subrounded-to-rounded sandy gravel units inglaciolacustrine landforms. We expect that Schmidt hammer measurements on recentlydeglaciated bedrock outcrops will reveal a decreasing surface weatheringtransect from distal moraines to present-day ice front showing a potentialcorrelation with external controlling factors. Our results will inform us aboutthe coupled influence of climate variations and proglacial environments inglacier recession rates and, especially, how proglacial lakes might enhanceclimate-driven ice withdrawal, yielding key insights for better understandingthe response of tidewater glaciers to the ongoing climate change and offeringempirical constrains for past glacier behavior and paleoclimate modelling.