Geology Reference
In-Depth Information
Chapter 21
The Cenozoic Era: Mammals
Take Over
In This Chapter
Recognizing recent geologic events
Seeing how mammals have flourished
Following the path toward your own existence
The Cenozoic era of earth's geologic history hasn't ended yet. It began 65.5 million years
ago and continues today. Compared to previous geologic eras, the Cenozoic (so far) is rel-
atively short. But because it's the most recent era, scientists have access to a huge
amount of geologic and fossil evidence documenting its events.
Some geologists separate the Cenozoic era into two periods: the Tertiary (from 65.5 to 2.6
million years ago) and the Quaternary (from 2.6 million years ago to the present).
However, the Cenozoic is more commonly separated into three periods: the Paleogene
(65.5 to 23 million years ago), Neogene (23 to 2.6 million years ago), and Quaternary
(from 2.6 million years ago to the present).
In this chapter, I explain a few of the major geologic events of the Cenozoic in North
America and describe the fossil history of the rise of mammals. Entering the Cenozoic
era, you enter the Age of Mammals and (eventually) humans.
Putting Continents in Their Proper (Okay,
Current) Places
At the beginning of the Cenozoic era, the major continents were pretty much positioned
the way they are today, with the exception of parts of Europe, Asia, and the Indian sub-
continent. The major mountain ranges of the modern world were formed during the last
