Historically, geologists have divided the Cenozoic into two Periods: Tertiary (65my-1.8my) and the Quaternary (1.8-present). The Tertiary was further divided into the Epochs: Paleocene, Eocene, Oligocene, Miocene and Pliocene and the Quaternary includes the Pleistocene and Holocene Epochs.

More recently the Paleogene world includes Paleocene, Eocene and Oligocene.  The later Miocene, Pliocene, Pleistocene and Holocene Epochs were then lump together to form the Neogene.

Worldwide events

Terrestrial and freshwater animals after the dinosaur extinction were represented by rapid radiation of mammals. The first carnivorous mammals appeared by the mid-Paleogene by the end of Paleogene.

Climatic change and mass extinction. During the Paleocene climate was warming, with very warm sea temperature even in arctic areas at the boundary between Paleocene and Eocene. The warmness of the polar water disturbed vertical circulation of water and caused the mass extinction due to anoxic environment. The Green River Formation of Wyoming/Utah is an important feature of this time period

Regional events

Western North America experienced continued to experience the Laramide Orogeny, which began during the late Cretaceous (100mya) and continued through the Paleogene.  This mountain building event is responsible for the formation of the North American Rocky Mountains  The Laramide Orogeny is characterized by low angle of the subduction that developed during the Sevier stage. Today in the Rockies we can observe the results because of erosion and isostatic uplift. Complicated collision of the three plates caused clock-wise rotation of the Colorado plateau. Yellowstone National Park Volcanism began during Eocene featured active volcanism with petrifying forest in lava.

The Gulf coast in Eocene featured Mississippi Embayment that develop in failed rift and Mississippi river delta started during Oligocene as the sea withdrew.



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