The John Day Fossil Beds capture over 40 million years of central Oregon’s plant and animal life. As the hot, wet semi-tropical climate (shown in the Clarno Nut Beds), became cooler and drier, new plants and animals evolved. The earlier semi tropical forests changed to more open hardwood forests mixed with lakes and swamps (seen in Turtle Cove fossils). By 7 million years ago, these hardwood forests shifted to the tall grasslands and semi-arid shrublands of today.
Hot and Wet
From 54 to 39 Ma (million years ago), central Oregon was hotter and wetter than it is today, with about 10 feet of rain falling every year. Fossils from the Clarno Nut Beds show a semi-tropical forest filled with ancient relatives of walnut, magnolia, banana, and palm trees. Crocodiles, 3-toed horses the size of dogs, cat-like mammals, and rhino-like Brontotheriids roamed these dense forests. These fossils were preserved as massive mudflows of ash and debris flowed down a nearby volcano, covering the semi-tropical forests and the animals and plants living in them.
Coldness sets In
As the hot, wet semi-tropical climate (recorded in the Clarno Nut Beds) of central Oregon became cooler and drier, new species of plants and animals evolved. About 33 to 24 Ma (million years ago), the earlier semi-tropical forests changed to more open forests mixed with lakes and swamps. Ancient relatives of elm, maple, and oak trees lived alongside Metasequoia (“dawn redwood”) trees. As the forests opened up, grasses started to appear. False saber-toothed cats, pig-like oreodonts, three-toed horses, bear-dogs, terminator pigs, tree squirrels, salamanders, and insects were preserved in layers of ash and pumice from nearby erupting volcanoes
Fossils Online
Check out some 3D scans of fossils that OMSI has collected from John Day. They are free to download!