Diggin' For Dinosaurs - Mill Canyon Dinosaur Trail
Mill Canyon Dinosaur Trail, Utah
The Mill Canyon Dinosaur Trail teaches more about palaeontologists than about dinosaurs. It offers an opportunity to see fossils in place, embedded in the rock matrix. Although plenty of ancient bones are visible along this quarter-mile trail, spotting them is a subtle art. The visitor soon gets a sense of the sharp-eyed patience a palaeontologists has to practice in the field in order to distinguish fossils from their surroundings, and figure out to which species a bone or fragment belongs.
During the late Jurassic, some 150 million years ago, parts of the now arid and rugged canyon country of southeast Utah were low-lying and wet. If discoveries from recent decades are any indication, they were also rich in dinosaurs. Four different species have been identified along this short stretch of Mill Canyon, and numerous bone pieces remain to be identified.
Many of the bones exposed along the trail belong to Camarasaurus, a large sauropod that grew to a length of 60 feet and a weight of 20 tons. Smaller but still hefty herbivores are represented by Stegosaurus, as famous for its tiny brain as for the rows of large plates running down its back, and by Camptosaurus, fast-moving and some 20 feet long. These plant eaters were probably preyed upon by Allosaurus, a powerful carnivore.
Visitors to the trail can see where grayish bone from these dinosaurs slowly erodes out of buff-colored rock; toward the end of the trail, pebbly conglomerate shows that some of the dinosaurs must have been buried among the fast-accumulating sediments of a riverbank or shoreline. Petrified wood is present, too. Neither wood nor fossil bone is protected by fences here, but resist the temptation to take souvenirs.
Numerous fossils of another sort are also present nearby, for the Moab area has lately become known as a hotbed of dinosaur tracks. Areas adjacent to Arches National Park, in particular, are rich in theropod tracks that may have been made as the sea rose along a flat shoreline, continuously wetting new tracts of sand that were traversed by numerous animals. One dinosaur track expert has estimated that more than a billion tracks may be present here (though only a small fraction are exposed on the surface), all contained in a single sandstone layer over an area of 300 square miles. From the Mill Canyon Trail, you can look eastward to the fiery red sandstone of Klondike Bluffs, home to an extensive dinosaur trackway.
Another site just northeast of Mill Canyon is marked and accessible to the public. Road construction here about three decades ago removed soil from a flat, slightly tilted sandstone pane that reveals impressions of a large sauropod and several carnivorous theropods. Deeply embedded in the rock, and with a diameter about that of an oil drum, the sauropod tracks show that their maker swerved sharply to the right, a rarely noted phenomenon. One of the theropod trails is also unusual, because the animal that made it had an irregular stride: there are alternating gaps of four and five feet between track marks. It's possible that the animal was injured and limping. That such individual markings should survive one-and-a-half million centuries is nothing short of astonishing.
The landscape around Moab is rugged, and much of it is quite difficult to reach; undoubtedly more fossil sites have yet to be discovered. For now, area visitors can most comfortably complete their prehistory circuit by visiting the Bureau of Land Management office in town. A large slab of 200-million-year-old sandstone displayed just outside the entrance is heavily marked with signs of ancient animals. Along with small dinosaur tracks are scorpion traces and the impressions of the wide feet of a mammal-like reptile named Brasilichnium: indicators of the diversity of life here in the distant past.