Our second day in Colorado had us traveling back down the Rocky Mountains into the Front Range. Our first stop was the Red Rocks Park and Amphitheater to see the Great Unconformity, a period of 175 million years eroded from the rock record. The bottom of this feature is composed of the Idaho Springs formation, a Precambrian Gneiss. Directly above this is the Fountain Formation, a sandstone composed of sands, pebbles, and cobbles which eroded off of the Ancestral Rockies.
This unconformity has raised many questions on how you erase millions of years of rock off of the face of the earth. Dr. Jeremy Caves Rugenstein explained to us that the leading theory of this disappearance is the occurrence of a Snowball Earth. During this time, Earth was completely covered in ice, even down to the equator. The ice which laid across what is now western United States scraped off rock above the basement Idaho Spring Formation, leaving us with a major jump in time until the Fountain Formation was deposited.
Our next stop at Red Rocks National Park took us through a nearby hiking trail to a promontory where we learned about the rock formations above the Fountain. Here the Lyons, Lykins, and Morrison could be seen in the valley below us, and gave a history of the the area spanning back to the Permian through the Jurassic. Where we were standing was once an inland sea called the Western Interior Seaway. My favorite rocks, stromatolites, could actually be found in the Lykins. Stromatolites are fossilized microbial mats. Early stromatolites are the oldest fossils on Earth. These stromatolites, however, are much younger than their billion year ancestors, and formed in a hypersaline environment. They give us information on what the environment was like here in Colorado during the late Permian, early Triassic.
Our last stop for the day took us to Dinosaur Ridge. Here we rented a bus to drive up and down the park, which spanned the Morrison and overlying Dakota formations. Our tour guide, “Pterano”Don talked about the different dinosaur prints that could be found in the Dakota Formation and how paleontologists interpreted the scenes imprinted into the rock. Tracks from hadrosaurs, ornithomimids, and crocodiles are found running up the eastern side of the the ridge (which was once a beach). On the opposite side of the ridge, footprints from a raptor, Allosaurus, and Apatosaurus are depressed into mud layers.
The last thing we saw at Dinosaur Ridge were the bones of Jurassic dinosaurs encased in sandstone. This was the location that Stegosaurus, Allosaurus, Apatosaurus, Diplodocus, and Iguanodon were found. Dinosaur Ridge played an important role in the Bone Wars between Dr. Cope and Dr. Marsh. This location, researched by Marsh, was almost destroyed by him to keep the fossils here from falling into his rivals hands. Thankfully, the site was saved and soon opened to the public so that people today could enjoy the scientific discoveries once hidden in the rock.
Written by Evan Ritchey