Reconstructing Plio-Quaternary fluctuations of the East Antarctic Ice Sheet in Terre Adélie inferred from cosmogenic nuclides (10Be-26Al) in glacially-polished bedrock, morainic boulders and nunataks

The East Antarctic Ice Sheet (EAIS) contribution for future global sea level rise and climate change is source of uncertainty, and it appears essential to reconstruct its past fluctuations. Previous works reveal geomorphic and chronological evidence that the ice sheet extended to the continental shelf break during LGM (Last Glacial Maximum; ~20 ka). However, still little is known about its response to the major climate and oceanic transitions following the LGM. In this study, we reconstruct (1) a chronology of ice-sheet fluctuations, (2) ice-sheet past erosion efficiency and (3) ice-sheet thinning during the late-Pleistocene to Holocene time-period, in Terre Adélie (East Antarctica). Newly obtained exposure ages for coupled ¹⁰Be-²⁶Al support a scenario of glacial fluctuations at global, regional and local scales. Inland nunataks reveal some long-term exposure with apparent exposure ages ~150 ka, while coastal areas record a past ice-sheet thinning after ~20 ka. Ages measured on erratic boulders of Archipel Pointe Géologie record the final episode of a regional deglaciation around ~15 ka. Slightly inland, in Lacroix sector, erratic boulders record a more recent local ice-sheet oscillations around ~1.5 ka. In contrast, exposure ages obtained on glacially-polished bedrock are characterised by spatially-variable inheritance, suggesting that past ice sheet retreat history is characterised by variations in erosion efficiency. Finally, our results also suggest some potential previous geomorphological inheritance from the hot Pliocene phase.