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:: Home > The People > Biological Legacy: The Forest > Eo/Oligocene


million years ago

The Eocene and Oligocene Periods of Geologic History

The Eocene occurred from 63 million until about 36 million years ago— the Oligocene continued to 25 million years ago. Oregon's major mountain ranges still hadn't formed, so fossil records are similar across the state and show the presence of palm, cinnamon, fig, avocado, trees, giant ferns, and the dawn-redwood.

By the Oligocene, land mammals and plants bagan looking like what we see today (although the trees now might be found in the temperate eastern United States or Asia). In central Oregon the trees were maple, oaks, elm, basswood, sycamore, gingko, katsura, and dawn-redwood (the latter three are now only found in parts of Asia).

Three-toed horses, camels, giant pigs, saber-toothed cats, and tapirs prowled the landscape. Oregon was definitely changing from a more tropical climate to the temperate one we know and love today.

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