Dinosaur Triangle in Western Colorado Rich in Fossils

by George Oxford Miller and Carole Price

We walk carefully through the graveyard. Bones, old bones, lie scattered on the ground — bones of creatures who roamed the earth 140 million years ago. We’re searching the barren soil for fragments that wash down the narrow gully after thunderstorms. A thick strata of crumbling clay on the hillside sheds bones like a fractured casket. Colorful pieces of petrified wood and agates mix with the bones and pebbles of worn sandstone and mudstone. Like gold-crazed miners who just discovered a mother lode of nuggets, we can’t take our eyes off the ground. "Look over here," says Kathy Bell, owner of Jurassic Tours. We gather around a bone protruding from the soft soil. "It’s a femur, probably an Apatosaur, a large plant-eating dinosaur." She kneels and carefully scoops away dirt with her hand. The leg bone dates from a time when the surrounding desert was a humid flood plain and the largest mammals were mouse-sized critters.

"It looks like it’s a loose bone by itself. We’ll see an articulated skeleton farther up on the slope." She gently covers up the fragile bone.

We had signed up with Jurassic Tours to spend the day exploring Rabbit Valley, 30 miles west of Grand Junction, Colorado, a part of the Dinosaur Triangle of western Colorado and eastern Utah. The largest and smallest dinosaurs come from this fossil-rich area, as well as the more recently discovered Utahraptor, described in scientific literature as "the ultimate killing machine." Some 30 species have been discovered in the immediate vicinity of our hike. The array of dinosaur specimens prompted the Bureau of Land Management to set aside 286 acres as the Rabbit Valley Research Natural Area.

The three of us thread single file up a sandy slope to a ridge overlooking the valley. Gnarled juniper trees and sage brush offer scant cover for wildlife. A startled rabbit scampers around a large boulder, reluctant to relinquish its shade. Or maybe it knows instinctively that the shadows floating across the ground represent danger — three golden eagles circling overhead.

Eons of wind and rain have eroded these hills like a potter shaping soft clay. Deep gullies expose the multi-colored sediments of the Morrison Formation, the geological strata that contains most of the fossils in the Dinosaur Triangle. A muted palette of grays and browns and crumbled reds paint the dissected landscape. Desert varnish — or, magnesium oxide — blackens sun-baked rocks exposed for thousands of years to the desert glare. Red and green lichens splatter the rocks, adding a contemporary pattern to the Jurassic motif.

Harder, more weather-resistant strata overlay the softer mud and sandstones and form the protective caps of pedestals and steep-walled ridges. When the softer layers melt away, the more resistant boulders tumble like Humpty Dumpty down the slopes. Beneath one of the resistant layers, Kathy shows us the skeleton of a Stegosaur, the state dinosaur of Colorado. Its vertebrae protrude through the soft rock, then disappear deeper into the earth.

The large, fractured boulder that gave the Split Rock fossil site its name rests on the ridge above the gully. The 10-foot wide sandstone conglomerate split in half to reveal a treasure-trove of sauropod bones. Huge femurs, vertebrae and ribs polished by millennia of blowing sand glisten in the afternoon sun. We run our hands over the ancient legs and necks and tails and wonder at the creatures that once thundered across these hills.

"The cluster of bones are bunched together in a glob of mud," Kathy tells us. "Since they’re in no order, there’s no scientific reason to chisel them out to the sandstone. Kids love to climb on the rock and get their pictures made with the bones." So do adults. From our vantage on the hillside, we can see across Rabbit Valley to the Museum of Western Colorado dinosaur quarry. The museum offers summer programs for the public to participate in the dig. The self-guided Trail Through Time loops 1.5 miles over a small hill and through an ancient stream channel. The 14 points of interest identify the plant-eating Apatosaurus, Diplodocus and Brachiosaurus. Portions of a Camarasaurus skeleton and plant fossils are also visible.

Jurassic Tours also takes people to a dig site with layers of slate that contain leaf and insect fossils. The Green River formation is exposed on the top of Douglas Pass, at 8000 feet. During the Eocene Epoch, a complex of lakes existed in western Colorado, eastern Utah and southwestern Wyoming. Sediments deposited in those lakes form the Green River Formation and contain the fossils of numerous plants and animals. You can pry apart the plate-like strata, and best of all, keep any non-vertebrate fossils you find.

"The site is so rich we always find lots of fossils," Kathy says. She shows us page-sized sheets of slate etched with the impressions of ancient leaves. "I took a father and son to Douglas Pass yesterday. I’m cleaning these up to ship them back to them." On the way back to Grand Junction, we stop in the town of Fruita at the Dinosaur Journey Museum of Western Colorado. A guide takes us through the paleontology laboratory and shows us the intricate steps involved in stabilizing and preserving the fragile fossil bones. Then, we visit the dinosaur gallery with its robotic dinosaurs typical of the area 140 million years ago.

As we walk through the exhibit, the bones we saw scattered over the parched landscape come to life. A Dilphosaurus spits a stream of water, a huge Brontosaurus looks up from its browse, and a flesh-eating Utahraptor roars over his prey. The bleached bones were abstract, a disjointed relic of time, and these creatures are just artist representations. Yet the combination of real and fantasy stimulates our imagination and gives us a new respect for the creatures that once dominated the world.

More Information
The Museum of Western Colorado schedules digs June through August for a fee, call 1-888-488-DINO.

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Hunting Dinosaurs in the Deserts
Desert Dinosaur Hunting Grounds

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