Why do scientists debate the date when the Drake Passage opened?

The opening of the Drake Passage between South America and Antarctica was a pivotal event in the Cenozoic Era, as it facilitated the development of the Antarctic Circumpolar Current and thermally isolated the continent.12

Scientists debate the exact timing of this opening because geological evidence allows for different interpretations regarding when a deep-water connection was fully established. There is significant disagreement among experts:2

• Early Estimates: Some researchers argue that the passage opened as early as the Eocene Epoch, approximately 41 million years ago.2
• Late Estimates: Other experts maintain that the event occurred much later, near the boundary between the Oligocene and Miocene epochs, roughly 23 million years ago.2

This uncertainty stems from the complexity of reconstructing ancient tectonic movements and the difficulty of determining when the passage became deep enough to significantly alter global oceanic circulation patterns.12