A large-scale transcontinental river system crossed West Antarctica during the Eocene

Area of Science:

• Paleoclimatology
• Paleogeology
• Geochronology

Background:

• Antarctica's extensive ice cover hinders understanding of its pre-glaciation history.
• Knowledge of pre-glacial environmental and tectonic development is crucial for comprehending the transition to the modern icehouse world.

Purpose of the Study:

• To investigate tectonic and topographic conditions in Antarctica during the Eocene epoch, preceding major ice sheet formation.
• To reconstruct the pre-glacial environmental conditions and geological development of West Antarctica.

Main Methods:

• Geochronological analysis of drill core samples from the Amundsen Sea shelf.
• Sedimentological analysis to determine depositional environments and paleoclimate conditions.

Main Results:

• The Eocene epoch (44-34 million years ago) marked a transition from tectonic quiescence to the reactivation of the West Antarctic Rift System.
• Incipient volcanism and the rise of the Transantarctic Mountains occurred during this period.
• Sediments indicate a coastal-estuarine swamp environment fed by a large river system, suggesting West Antarctica was largely above sea level but with low topography.

Conclusions:

• Low topographic relief and elevation in Eocene West Antarctica inhibited widespread ice sheet formation despite being above sea level.
• The findings provide critical insights into the geological and environmental factors preceding Antarctica's major glaciation.