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Mitchell area, Wheeler County, land of Oregon’s geologic roots

The photograph, taken from a point near the junction of State Highway 207 with U.S. Highway 26 just west of Mitchell, offers a view to the southwest toward Bailey Butte in the foreground, White Butte behind it, and the north flank of the Ochoco Mountains in the background.

Here we are on the southwestern edge of the Blue Mountains province and in a region whose underpinnings contain some of the oldest rocks and fossils of the state. These basement rocks are considered to be part of the Baker terrane—fragments of 250-million-year-old oceanic islands that wandered a long way across the ancestral Pacific Ocean before crunching into the North American landmass near the Oregon-Idaho border. Thus began the process that extended the continent farther and farther to the west and created most of the land on which we live today.

Much of this area is underlain by Cretaceous marine sediments that were deposited in 100-million-year-old offshore basins The buttes seen in the photo mark the deeply eroded roots of 40- to 50-million-year-old volcanoes. Folding, faulting, continental volcanism, uplift, and erosion over the last 50 million years have combined to produce an extremely complex and interesting geologic province. (Photo contributed by one of our readers: Jamie Sands of Pendleton)

Access: Mitchell is situated about 50 mi east from Prineville on U.S. Highway 26, which crosses the entire state, from the northern coast near Seaside to the Idaho border at Ontario. From Mitchell, one can easily reach the three units of the John Day Fossil Beds National Monument: the Painted Hills Unit to the northwest, the Sheep Rock Unit (headquarters) to the east near Picture Gorge, and, a little farther, the Clarno Unit to the north.

Useful, if somewhat outdated guides, maps, pictures (great aerial view of Mitchell!), and exploration hints, can be found in an unpretentious booklet produced by the Geological Society of the Oregon Country for its President’s Campout in 1969 ($1 at the Nature of the Northwest Information Center).




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Oregon Department of Geology and Mineral Industries
800 NE Oregon Street, Suite 965, Portland, OR 97232-2162
(971) 673-1555, FAX (971) 673-1562
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