LGM - Holocene West Antarctic Ice Sheet evolution by multidisciplinary analysis of five gravity cores collected in the Glomar Challenger (Eastern Ross Sea, Antarctica)

The history of the Western Antarctic Ice Sheet (WAIS) during the Last Glacial Maximum (LGM) – Holocene transition is still debated. The most accepted interpretation is that the WAIS was grounded near the shelf break during the LGM (e.g., Halberstadt et al., 2016; Anderson et al., 2018; Gales et al., 2021). An alternative hypothesis was proposed by Bart & Owolana (2012): the ice sheet was grounded in the middle shelf during the LGM and morphologies identified at the shelf break were formed during previous glacial cycles. Timing and mechanisms of the last glacial retreat are still under investigation. Here we present the preliminary results of a transect of five gravity cores collected in the Glomar Challenger Basin (Eastern Ross Sea, ERS), from the inner continental shelf to the shelf break, in the framework of several PNRA expeditions. The reconstruction of sedimentary dynamics and paleoenvironmental evolution is based on a multidisciplinary approach: sedimentological, geochemical (XRF), micropaleontological and biomarker (IPSO25) analyses and physical properties. Accelerator Mass Spectrometry (AMS) is used to date the gravity cores using organic matter. Three phases have been identified, representing the evolution of the Glomar Challenger since the LGM: a glacial phase represented by subglacial diamicton (heterogeneous and overcompacted sediments), a glacial-marine phase represented by sub-ice shelf ice rafted debris-rich sediments and the Holocene characterized by muddy sediments.