John Day Fossil Beds

Most fossil sites are a single moment. This one is a sequence, and that is what makes it rare. The John Day basin stacks more than 40 million years of the Age of Mammals in readable order, and the Park Service has given the layers names you can walk between.

Start at the Clarno Nut Beds, 44 million years back, when Oregon was hot, wet and semitropical, growing palms and avocados. Move up to the Hancock Mammal Quarry at 40 million years, cooler and drier but still frost-free. At Bridge Creek, 33 million years ago, fine lake sediment caught a great range of plant material including Metasequoia, now Oregon's state fossil. Turtle Cove, 30 to 25 million years, is the thickest and most productive layer in the monument, though it kept few leaves. By the Upper John Day, 24 to 20 million years, the country had opened out and the animals had become burrowers and runners. In the Mascall beds at 15 million years, long-legged horses, camels and giraffe-deer were crossing meadows with beardogs and cats behind them. By the Rattlesnake assemblage at 7 million years the scene looks almost modern, apart from the occasional elephant and giant sloth.

The palaeontologist Ralph Chaney said no region in the world shows a more complete sequence of Tertiary land populations, plant and animal alike, than the John Day Basin.

The science here started in 1864 with Thomas Condon, a missionary and amateur geologist who recognised what the rocks held and told the world about it. Parts of the basin became a national monument in 1975. Today it is three separate units, Sheep Rock, Painted Hills and Clarno, totalling 13,944 acres of semi-desert shrubland, riparian corridor and banded badlands, with the Clarno Unit sitting 18 miles west of the town of Fossil. Around 210,000 people came in 2016. Fossils stay where they lie: this is National Park Service ground, and the Thomas Condon Paleontology Center is where you get to look closely.