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2.23: Cenozoic Era

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    Cenozoic Era

    The Cenozoic is commonly referred to as the Age of Mammals. The Cenozoic Era began with the mass extinction event associated with the K/T Boundary (discussed above). Highlights of the Cenozoic Era include:
    • Dominant large animals: Mammals. Mammals diversified, gradually replacing the niches held by dinosaurs wiped out by the K/T extinction.
    • Mountain building continued, especially around the Pacific Ocean; the Himalayan Mountains, the Alps, and mountain ranges throughout southern Eurasia begin to form. The Rocky Mountains and Cordilleran Ranges in western North America continued to form.
    • Lots of erosion of existing mountains fed sediments to coastal plains and ocean margin basins.
    • The youngest Tejas Sequence began to accumulated in the early Cenozoic Era and continues to the present day, forming the Atlantic and Gulf Coast regions.

    The Cenozoic Era is generally divided into two (or three) periods:



    Time Range


    Tertiary Paleogene 66 million to 23 million years ago
    Neogene 23 million to 2.6 million years ago
    Quaternary 2.6 million years ago to the present

    The older name, Tertiary Period, in now subdivided into two periods: Paleogene Period and Neogene Period.
    The periods of the Cenozoic Era are also subdivided into time periods called epochs.

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