Eocene - Palaeogeography

Palaeogeography

During the Eocene, the continents continued to drift toward their present positions.

At the beginning of the period, Australia and Antarctica remained connected, and warm equatorial currents mixed with colder Antarctic waters, distributing the heat around the planet and keeping global temperatures high, but when Australia split from the southern continent around 45 Ma, the warm equatorial currents were routed away from Antarctica. An isolated cold water channel developed between the two continents. The Antarctic region cooled down, and the ocean surrounding Antarctica began to freeze, sending cold water and icefloes north, reinforcing the cooling.

The northern supercontinent of Laurasia began to break up, as Europe, Greenland and North America drifted apart.

In western North America, mountain building started in the Eocene, and huge lakes formed in the high flat basins among uplifts, resulting in the deposition of the Green River Formation lagerstätte.

At about 35 Ma, an asteroid impact on the eastern coast of North America formed the Chesapeake Bay impact crater.

In Europe, the Tethys Sea finally vanished, while the uplift of the Alps isolated its final remnant, the Mediterranean, and created another shallow sea with island archipelagos to the north. Though the North Atlantic was opening, a land connection appears to have remained between North America and Europe since the faunas of the two regions are very similar.

India continued its journey away from Africa and began its collision with Asia, folding the Himalayas into existence.

It is hypothesized that the Eocene hothouse world was caused by runaway global warming from released methane clathrates deep in the oceans. The clathrates were buried beneath mud that was disturbed as the oceans warmed. Methane (CH₄) has ten to twenty times the greenhouse gas effect of carbon dioxide (CO₂).