LAUSR

Modeling the early development of the West Antarctic Ice Sheet (WAIS) hinges on the configuration and evolution of Paleogene terrestrial landscapes associated with the West Antarctic Rift System. A widely applied but previously untested paleotopographic reconstruction for the Eocene/Oligocene boundary suggests that much of central West Antarctica was as much as 1,000 m above sea level at that time, constituting a key nucleating site for an early WAIS. Here we show that Paleogene age marine and terrestrial microfossil assemblages and biomarkers in sediments recovered from beneath the WAIS provide direct evidence contrary to this widely utilized “maximum” paleotopographic reconstruction. These new constraints call for significantly modified tectonic and ice sheet model parameterization and also provide insights into modern differential uplift across the West Antarctic Rift System.