Geochemical characterisation of the Ellsworth-Whitmore Mountains crustal block: a critical piece in the puzzle to unravel ice retreat in West Antarctica

The West Antarctic Ice Sheet (WAIS) is prone to major retreat. Identifying when previous WAIS retreats occurred could improve sea level rise projections, but detection of these events in marine sediments is limited by knowledge of the geochemical signature of key sediment source regions located further inland - primarily the Ellsworth-Whitmore Mountains (EWM). This is because a smaller WAIS would likely result in enhanced erosion of the EWM and permit more widespread transport of EWM detritus offshore. We here characterise the provenance signature of the EWM, showing that different stratigraphic units exhibit distinct geochemical characteristics based on unique combinations of zircon U-Pb ages and Nd and Sr isotope ratios. The oldest Heritage Group displays dominant Grenville Orogeny (1000–1250 Ma) ages, with mean ε Nd values of ∼ − 8 and 87 Sr/ 86 Sr ratios of ∼0.719. The overlying Crashsite Group and Whiteout Conglomerate exhibit dominant Ross Orogeny ages (490–580 Ma), with mean ε Nd values of ∼ − 12 and − 18 and 87 Sr/ 86 Sr ratios of ∼0.740 and ∼ 0.725, respectively. The youngest Polarstar Formation has common Permian zircon U-Pb ages and ε Nd values of ∼ − 4 and 87 Sr/ 86 Sr ratios of ∼0.711. Outlying nunataks are assigned to the Heritage and Crashsite groups, extending our geological knowledge of the Ellsworth Subglacial Highlands. Together, our data suggest that the Ellsworth Mountains crustal block is characterised by a mean ε Nd value of ∼ − 10, 87 Sr/ 86 Sr ratio of ∼0.728, and bimodal Ross and Grenville orogeny zircon U-Pb ages. This “provenance fingerprint” should be identifiable in offshore sediments recording times of major WAIS retreat.