New research, published in the journal Nature, suggests that West Antarctica was likely a river delta or estuary during the Eocene epoch, around 56 to 34 million years ago. This finding challenges previous assumptions that the region was covered by a vast ice sheet during this time period.

The study analyzed core sediment samples collected from beneath the West Antarctic Ice Sheet, which is currently the largest ice sheet in the world. These samples revealed the presence of plant fossils, pollen, and other organic materials that are typically associated with river delta or estuary environments.

According to the researchers, this evidence suggests that West Antarctica was once a warmer region with a climate that was more conducive to plant growth. They propose that the West Antarctic Ice Sheet may have formed much later, during the Oligocene epoch, which began around 34 million years ago.

The findings of this study have implications for understanding the history of the Earth's climate and the role of the West Antarctic Ice Sheet in sea level rise.