On a recent trip to New Mexico, before we had to hustle back home, we visited an exposed dinosaur trackway in the north-east corner of the state.
For me visiting these sites is an experience in time travel as much as it is in science. The tracks at Clayton Lake State Park were made in the early Cretaceous period about 100 million years ago. At this time in Earth’s geology, the main continents that we know today had been separated from the Pangea supercontinent of 250 million years earlier and were roughly in shapes that are recognizable today. At the time the tracks were made the current continent of North America was divided by a shallow sea that ran from the Arctic area to the current Gulf of Mexico. This sea is known as the Western Interior Seaway. Its western shore ran along the eastern area of the Rocky Mountains. The western portion of the Seaway covered the states of Texas, Colorado and Wyoming as well as much of Montana, Utah, and New Mexico. Throughout the 79 million years of the Cretaceous period the seaway rose and fell, receding from and later re-covering areas of shoreline.
Along this shoreline walked the dinosaurs. They lived in what was likely a marshy area of damp soils in which their footsteps would create massive footprints that can now be seen in several areas along what was the western boundary of the Western Interior Seaway. This western boundary now contains what is called the Dakota Group of rock which was laid down by the silts of the Western Interior Seaway.
The trackway at what is now known as Clayton Lake State Park was discovered after a large rain event in 1982. The dam which forms Clayton Lake was built in the 1950s and improved in the 1970s. The dam captures the water of the Seneca Creek which is held behind the dam. The dam is 92 feet high and 150 feet long with a broad walking path on the top. This path leads to the dam’s spillway on its northern end. This is where the dinosaur footprints may be seen. When the dam was built a spillway was cut out of the adjacent hillside so that the dam would not be damaged by heavy rain events. In that type of rain event, the lake may become filled to near the crest of the dam. The adjacent spillway allows water from the lake to be channeled around the side of the dam so that it is not over-topped by the rising water. In 1987 as the water rose it flowed over the spillway in torrents large enough to carry away the layers of rock and dirt that overlay the bottom of the spillway.
I imagine that I can see that storm and the rising water in the lake. The overflow from the lake flows across the spillway, cutting away material above the dinosaur footprints and exposing them. Now as I look out, I can see the herd of dinosaurs moving up the shore of the lake. Large hadrosaurs, believed to have been Iguanodons, slowly walk past me moving north along the shore of the Western Interior Seaway. They browse on the vegetation that grows along the shore . Some splash out into the shallows of the water to eat the submerged vegetation that grows there. A baby Iguanodon scurries past me looking around for its parent. As it passes, a crocodile, swims up through the shallows looking for a meal, perhaps something about the size of the small Iguanodon that just passed. The crocodile is too small to be a threat to the adults, but it is large enough so that as it lies in the shallows, watching, the adult Iguanodons move around it. As I stand watching, the beasts in the herd flow around me, large bulls, adolescents, females, and scurrying so as not to be stepped on a number of the baby Iguanodons. They move past me on their way up the shore of the vast inland seaway.
In the failing light of the day they continue their trek. I can barely see them through the mist and slight rain that seems to continually fall. Suddenly, ahead, I hear excited chirps and calls from the herd. A great roar is heard ,and the Iguanodons can be heard splashing in the shallows as they surge into the lake. A carnivore, a meat eater, known now as an Acrocanthosaurus, can be seen coming out of the taller vegetation farther from the shore, and moving slowly towards the herd. It moves north following the herd of herbivores, plant eaters. Soon the herd and the stalker disappear into the mists and failing light.
I find myself still standing on the walkway that surrounds the dinosaur footprints, looking down the footprint left by the Acrocanthosaurus. I am back in the present. I look out across the arena where these creatures walked over 100 million years ago.
Pictures of these dinosaurs may be found at; Acrocanthosaurus at http://www.emnrd.state.nm.us/SPD/claytonlakestatepark.html and Iguanodons at https://www.newdinosaurs.com/131_iguanodon_raul_martin/
Information on the New Mexico Clayton Lake State park may be found at http://www.emnrd.state.nm.us/SPD/claytonlakestatepark.html , https://geoinfo.nmt.edu/tour/state/clayton_lake/home.html , and https://ucmp.berkeley.edu/mesozoic/cretaceous/clayton.html .
