资源环境科技发展态势分析平台

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.

Plain Language Summary The configuration and elevation of Antarctic land masses played a key role in early ice sheet development in a world with CO2 much higher than today's. Several studies have attempted to reconstruct the terrestrial landscape of the tectonically complex West Antarctica 34 million years ago, a time when a cooling climate led to Antarctic ice sheet growth. Here we use sedimentary records collected from beneath the West Antarctic Ice Sheet interior to test published landscape reconstructions for this critical interval in Earth history. Marine microfossils (diatoms, dinoflagellates, calcareous nannofossils, and ebridians) are used to constrain the ages of sedimentary deposits. Additionally, we use terrestrial pollen, spores, and freshwater diatoms, as well as marine and terrestrial organic biomarkers, to document past sedimentary basins and reconstruct paleoenvironments during the transition from the warm Eocene (similar to 56 to 34 million years ago) to the cooler Oligocene (similar to 34 to 23 million years ago). Our results significantly advance knowledge of tectonic and landscape evolution across West Antarctica, thus calling for improved modeling of the early ice sheet.