About the Route – Classic XXXII Day 4

Day 4 plays tricks on your mind, in a good way. We ride through wide-open farmland, rolling hills, pine forest, towering canyons, wide expanses with hills and mountains looming in the distance – and all within 43.9 miles. The Twickenham area is particularly perplexing. A fortress of rock surrounds the valley and plateaus ring the skyline. Where is this place? Colorado? Utah? Arizona? Mars? Nope, it only exists in Oregon. And the hands-down best way to experience it is by bicycle. 

Day 4: Fossil to Mitchell

Main Route: 44.6 miles / 3,914’ elevation

Day 4 is another big bite of the Painted Hills Scenic Bikeway with the emphasis on s-c-e-n-i-c! We’re all on the same route and we’re heading to one of our favorite places, Mitchell, Oregon. We like it so much we made the route a giant “M” – Up-Down-Up-Down. Roll south in the morning on the John Day Highway and power your way to the mini-M twin summit near Service Creek. From here we zig-zag downhill along Rowe Creek Road, dropping through Beard, Walker, Dedman, Bull and Thompson Canyons before leveling out into Twickenham Canyon. It’s here that we say hello to the John Day River once again, crossing the cleverly named John Day River Bridge (1963) as the road points up once again paralleling Girds Creek and rolling through Black Canyon. Summit this final climb on the shoulders of Sutton Mountain and prepare for the lumpy mostly-down-but-a-little-up final line of our glorious “M”. Yes, that means Mitchell is waiting and it will be our two-night layover home.

Ah, Mitchell, how we love thee! It’s called the Gateway to the Painted Hills but also lays claim to 100-year-old fossils of herbivorous dinosaurs. You like to rock? Mitchell turns it up to 11. The city boomed in the late 1800’s as mining, ranching, and timber swelled the population. Despite being a small town, Mitchell had two distinct communities. The business district, was home to stores, five saloons, a flour mill, an apothecary, three houses of ill-repute, two hotels, and two newspapers. It could get rowdy here and ultimately earned itself the nickname “Tiger Town”. Built a little higher up on a plateau overlooking Bridge Creek was “Piety Hill” where many homes and churches were built. Take a walk through town and discover the Old West at its best!

Geology Rocks! by Ian Madin

Ian Madin worked as a geologist with the Oregon Department of Geology and Mineral Industries for 32 years and has ridden with Cycle Oregon for over a decade now. Here, he gives us a look at the the cool and sometimes hidden geology of the regions through which we ride. His nightly presentations at Classic are always fun and informative so grab a cold beverage or dessert (maybe both!) and grab a seat when we get him on the mic.

Be sure to read Ian’s Classic XXXII Geology Rocks! preview feature first. You can find it on our blog here.

About the Route Classic XXXII Day 1 is here.

About the Route Classic XXXII Day 2 is here.

About the Route Classic XXXII Day 3 is here.

View all Classic XXXII routes on Ride with GPS here

Descent into the depths of time – Today’s ride is by no means the longest of the week, but it covers the greatest amount of geologic time, from the 1920s to 280 million years ago. For most of the past few days the route has been passing back and forth across the unconformity between the 16-million-year-old Columbia River Basalt and the 30–40-million-year-old John Day and Clarno rocks. Today will takes us across two more unconformities with even bigger jumps into the past, and passes geologic events from the last century.

Leaving Fossil you will retrace your steps towards Service Creek, until the route turns off at the first snack stop onto Rowe Creek Road.  As you descend along Rowe Creek, you will start to see more colorful John Day ash and sediment layers, and as you get closer to the John Day River, you will start to see red-brown cliffs of Columbia River Basalt topping the ridge on the left side of the road and ahead of you, which means that you are still well below the unconformity.  

The ride down Rowe Creek is through John Day rocks, with patches of red and white ash layers visible where the soil and vegetation cover is thin. The unconformity and Columbia River Basalt cap the ridge to your left as you descend.

Once you cross the John Day River at Twickenham the entire landscape to the south consists of Columbia River Basalt, from the river to the top of the highest ridge.  This is Sutton Mountain, a block of Columbia River Basalt 14 miles long and 5 miles wide that stretches from Service Creek to Mitchell.  Climbing up Girds Creek, the road winds through beautiful cliffs of Columbia River basalt, many stained red by iron with patches of bright orange or chartreuse lichen. Columnar jointing is common, turning cliffs into palisades of naturally hewn rock. 

Girds Creek cuts a beautiful canyon through colorful Columbia River Basalt with bold cliffs displaying natural columns.

Keep your eyes peeled as you near Highway 207 for a few small outcrops of very different rock on the left-hand side of the road.  These areas of conglomerate, which looks like cemented river rock, are a hint of bigger changes to come. When you make the turn onto Highway 207, you cross the unconformity once again into the John Day rocks, but just a little way up the road you cross a second, much older unconformity, taking a 60-million-year leap into the past.  The route now leaves the John Day and Clarno volcanic rocks and enters into the age of the dinosaurs, represented by the Hudspeth Mudstone and Gable Creek Conglomerate. These are 100-million-year-old sedimentary rocks, deposited in coastal rivers and shallow waters off the coast of an ancient Oregon.  Along this stretch of road, you will mainly see conglomerate, which consists of rounded gravel cemented into a hard rock.  About a mile after you make the turn on to Highway 207, you will see big pillars and cones of conglomerate on the slope to your left.  These are remnants of a continuous thick layer shaped by erosion.  The erosion is guided by joints and fractures that have developed in the rock over their long journey to the surface.

A mile after the turn onto Highway 207, cones and pillars of 100-million-year-old conglomerate are visible on the left.

Your climb finally ends a few miles past the conglomerate cones and the road begins to descend through Meyers Canyon towards Mitchell.  About 2.7 miles from the summit, you will pass a deep gully on your right, whose vertical walls expose layers of sand and gravel, including a layer of white volcanic ash from the great eruption of Mt Mazama that formed Crater Lake 7,700 years ago.  There is a remarkable and mysterious story attached to this gully, which extends for miles down Meyers Canyon.  Some unknown geologic event 10-20,000 years ago caused the canyon to start filling with sediment, including the Mt. Mazama ash. This resulted in a broad, flat valley floor that was present when the first European settlers arrived in the region. Sometime during the 1920’s a catastrophic erosion event occurred, carving a vertical-walled gully 30-50 feet deep and 4 miles long up the canyon, removing much of the sediment that had accumulated in the last 20,000 years. There were no witnesses to this event, but the geologic wreckage leaves little doubt that it occurred. Both the rapid accumulation of sediment and the rapid erosion are highly unusual, adding to the mystery of Meyers Canyon. 

This deep gully along Highway 207 was formed during a mysterious erosion event during the 1920s. It extends all the way to the mouth of Meyers Canyon, four miles away, and is as much as 50 feet deep and 200 feet wide.

The mysteries aren’t done yet, because shortly after you pass the gully, you will cross a third unconformity and leap back another 180 million years to one of the exotic terranes that make up the deep geologic foundation of Oregon.  These ancient rocks originated as island chains in the Pacific Ocean, similar to modern day Japan, and were transported by plate tectonics for thousands of miles across the surface of the earth until they collided with the North American continent.  The violent collision welded the rocks onto the edge of the continent, and in the process layers of sandstone and limestone were dragged deep into the earth and then forced back to the surface.  This rapid journey to great depth and back results in a unique type of metamorphic rock, called blueschist.  The minerals characteristic of blueschist form at high pressure and low temperature. 

Climbing out of Girds Creek, the route crosses three unconformities in succession. The first is between the Columbia River Basalt and John Day rocks, the second separates John Day rocks from the much older Hudspeth mudstone and Gable Creek conglomerate, and the third provides a window int the 280-million-year old metamorphic rocks that make up the deepest levels of Oregon geology.

When a block of rock is pulled deep in the earth, the pressure increases immediately, but it takes a while for the temperature to increase as the heat slowly permeates the rock. Blueschist forms and is preserved if the rock is pushed rapidly back to the surface before it heats up, which is a rare circumstance that only happens in tectonic collisions.  This window into the depths of time and the earth only covers 100 acres, and in it the blueschist is mixed with marble that has been repeatedly fractured and healed on its tortuous journey. Similarly old exotic rocks underlie most of Oregon, but are usually covered with thick layers of younger rocks. After less than a mile the road passes back into the 100-million-year-old Hudspeth mudstone, which you will see on the left as you make the final descent to Highway 26 at Mitchell. 

These are polished samples of the 280-million-year-old marble (left) and blueschist from beneath the third unconformity.

For much of the way down Meyers Canyon you will also have a great view of Bailey Butte, which sits just north of Mitchell.  Bailey Butte is marked by bold cliffs of dark lava that form an arc across the top of the butte. This is another dike of Clarno Formation andesite, injected into the Hudspeth mudstone some 40 million years ago.

Bailey Butte which sits right above Mitchell, is made of ancient Hudspeth mudstone injected by a thick dike of Clarno andesite, forming a high cliff that arcs across the top of the butte.

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