Footprints in the sand may not seem like much of a legacy. Unless, of course, those footprints happen to endure 150 million years or so.
Such is the case near Moab where recent discoveries of literally thousands of unique dinosaur footprints near Arches National Park have prompted some scientists to apply normally unscientific descriptions such as "awe-inspiring" and "mind-boggling."In some places, as many as 2,000 tracks are in a one-acre area, often with a density of 10 tracks per square meter. Dinosaur tracker Martin Lockley, a University of Colorado geologist, now labels the sites near Moab as "undoubtedly one of the most important areas in the northern part of the Colorado Plateau."
And that has Bureau of Land Management officials looking at ways to protect the tracks - particularly where Jeep trails cut directly across them.
"We're looking for ways to balance public interest in dinosaurs with protection of a non-renewable resource," said BLM archaeologist Julie Howard. "And that can sometimes be a delicate balance."
Local officials are hoping to capitalize on the worldwide fascination with dinosaurs and, in the process, make Moab a key destination on the "Dinosaur Triangle" tourism promotion linking dinosaur museums, quarries and exhibits in Grand Junction, Vernal and Price.
A rare `megatracksite'
What Moab appears to have more of than any Dinosaur Triangle destination is dinosaur tracks. In fact, scientists now refer to one 10-mile-long area northwest of Moab as a "megatracksite" - one of only three anywhere in the nation.
Over the past few years, Lockley and the University of Colorado's Dinosaur Trackers Research Group has focused its attention on the Moab area, documenting scores of previously unknown fossilized animal track sites from many different periods in geologic time.
Of particular interest to scientists is a large number of carnivorous "theropod" tracks along a 15-kilometer Entrada-sandstone outcrop between the 210-million- to 230-million-year-old Chinle formation and the 150-million- to 160-million-year-old Morrison formation.
Traditionally, the Entrada Formation - responsible for the colorful rock formations of Arches National Park - has been regarded as devoid of fossil remains due to a Sahara-like desert that dominated the landscape.
"There certainly was a great western desert," Lockley said, "and evidence of water is largely restricted to localized deposits representing small playas or oases and streams. However, it was precisely these environments that supported and sustained life in this vast ancient desert and moreover provided the shorelines and water courses receptive to footprint formation."
The Entrada dinosaur prints are found just where the Entrada Formation meets the later Morrison Formation. Some of the same tracks are found in the lower levels of the overlying Morrison Formation.
A few dinosaur tracks from the Entrada Formation had been reported in the 1940s, but they were undocumented. So when Lockley heard rumors of dinosaur tracks in Moab-area formations, he traced the reports to the Salt Valley northwest of Moab. He found the tracks in 1987 and has been researching them ever since.
One million tracks
The extent of the discovery has astounded all who have seen it. Lockley believes the site to be part of a mostly covered "larger track-bearing complex that extends continuously over an area of several hundred square miles."
Which means that in the 30-mile drive from Crescent Junction to Moab, Lockley estimates a car 6-feet-wide would pass over as many as 1 million dinosaur tracks.
Professional dinosaur trackers still are unraveling the mystery of why tracks appear where they do and in varying degrees of frequency. Lockley admits the science of interpreting dinosaur tracks is still in its infancy, but he theorizes the favorable conditions were created when large, flat-lying areas of wet coastal plain get trampled by several generations of dinosaurs.
Geologists have identified a shallow gulf-like sea that encroached into Utah and was fringed by extensive mud and sand flats. "The density (of tracks) indicates several million tracks per square mile or literally billions in the entire megatracksite area," he said.
Dinosaur and other animal tracks are fairly common in the earlier Chinle, Wingate, Kayenta and Navajo formations, and the later Morrison formation.
Tracks like human hands
A Chinle Formation site near Canyonlands National Park south of Moab is dominated by the tracks of four-footed animals, called Chirotherium, whose hind feet had five toes and who left tracks resembling a human hand. But Lockley points out that of the 40 or so paths identified, only about four are attributable to dinosaurs - about 10 percent of the total animal population that left their mark on the ancient shoreline.
"They indicate that dinosaurs made up a relatively small proportion of the animal communities at this time and that many other types of reptiles were far more abundant," he said.
Unlike the Chinle, the later Wingate and Kayenta formations are dominated by dinosaur tracks, sometimes to the exclusion of all other animal tracks. These are represented mostly by the traditional three-toed variety.
The Navajo Formation again sees more variety of animals in the footprint record, including what Lockley refers to as doglike mammals called Tritilodonts.
It is the next period in the Colorado Plateau area, the Entrada Formation, that was previously believed to be devoid of life.
The Wingate, Kayenta, Navajo and Entrada formations - from a period that lasted 40 million to 60 million years - was typified by Sahara-like conditions where water was in short supply. But where water is found, so also are dinosaur tracks - more so than even the experts ever dreamed.