Age of Mammals. Paleocene, Eocene, Oligocene, Miocene, and Pliocene Epochs. During the Paleocene, the vast inland seas of the Cretaceous Period dry up, exposing large land areas in North America and Eurasia. Australia begins to separate from Antarctica, and Greenland splits from North America. A remnant Tethys Sea persists in the equatorial region.
Mammalian life diversifies, spreading into all major environments.
Eocene Epoch 55-34 million years ago Plate tectonics and volcanic activity form the Rockies in the western North America. Erosion fills basins, laying bauxite deposits in western North America. Continental collisions between India and Asia culminate in the Alpine-Himalayan mountain system. Antarctica and Australia separate and drift apart. The climate is subtropical and moist throughout North America and Europe.