Prehistory of Colorado provides an overview of the activities that occurred prior to Colorado's recorded history. Colorado experienced cataclysmic geological events over billions of years, which shaped the land and resulted in diverse ecosystems. The ecosystems included several ice ages, tropical oceans, and a massive volcanic eruption. Then, ancient layers of earth rose to become the Rocky Mountains.
Before humans, the dinosaur, mammoth, mastodon, camelops, and giant bison foraged for food in a verdant land. During the Ice Age summer, humans walked into the present Colorado area as they followed and hunted large animals.
The ancient hunters, the Paleo-Indians, evolved into modern Native American nations. The first people in Colorado were nomads, following and hunting large mammals using the Clovis point. As Megafauna became extinct, people adapted by hunting smaller animals, gathering wild plants, and cultivating food, such as maize. As the natives became more sedentary, there were significant technological and social advances, including basket, pottery, and tool making, and creation of permanent structures and communities. Trading with other indigenous people expanded the number and type of material items used for material goods, such as sea shells, stones for jewelry and tools, pottery and food.
Origins
Geological formations The following is a summary of geological formations in Colorado:
Precambrian igneous and metamorphic rocks Precambrian metamorphic rock that forms the core of the North American continent during the Precambrian eon 4.5–1 billion years ago. There is also Precambrian sedimentary argillite, dating back to 1.7 billion years ago. During the Paleozoic, western North America lay underneath a shallow sea, which deposited many kilometers of limestone and dolomite.
Pikes Peak granite
The Paleozoic era and during the Precambrian eon, about 300 million to one billion years ago, Pikes Peak Granite was formed from mass amounts of molten rock that would amalgamate, flow and combine, to form the continents. In Colorado it is known as the Precambrian Pikes Peak Granite. Over the next 500 million years, sedimentation (sediment deposition) occurred after the granite was produced. At about 500 to 300 million years ago, the region began to sink and lime and mud sediments deposited in the newly formed space. Eroded granite produced sand particles that formed strata, layers of sediment, in the sinking basin. At about 300 million years ago the land lifted, creating the ancestral Rocky Mountains.Johnson, Kirk R.; Raynolds, Robert G. (2006) Ancient Denvers: Scenes from the Past 300 Million Years of the Colorado Front Range. Fulcrum Publishing for Denver Museum of Nature and Science .
Fountain Formation
Fountain Formation was formed during the Pennsylvanian period of the Paleozoic era, 290-296 million years ago. Over the next 150 million years, during uplift the mountains would continue to erode and cover themselves in their own sediment. Wind, gravity, rainwater, snow, and ice-melt supplied rivers that ultimately carved through the granite mountains and eventually led to their end. Fountain Formation is Pennsylvanian bedrock unit consisting primarily of conglomerate, sandstone, or arkose, in Colorado and Wyoming, along the east side of the Front Range of the Rocky Mountains, and along the west edge of the Denver Basin. The characteristic predominant red color and the composition of the Fountain reflect that of the granites and gneisses from which it was eroded. Related sites are: Flatirons, Garden of the Gods, Red Rocks Park, Roxborough State Park
Lyons Formation
Lyons Sandstone was formed during the Permian period of the Paleozoic era, 250-280 million years ago. At the beginning of the period, sea levels were low and present-day Colorado was part of the super-continent Pangaea. Sand deserts covered most of the area spreading as dunes seen in the rock record, known today as the Lyons Sandstone. These dunes appear to be cross-bedded and show various fossil footprints and leaf imprints in many of the strata making up the section. Related sites include: Garden of the Gods, Roxborough State Park, and the Lyons and neighboring Hall Ranch Open Space areas.
Lykins Formation
Lykins Formation was formed during the Jurassic and Triassic periods 150-250 million years ago. The sediment deposition of wavy layers of muddy limestone and signs of stromatolites that thrived in a smelly tidal flat at present-day Colorado. The Ancestral Rockies were burying themselves while the shoreline was present during the break-up of Pangaea. This formation began right after Earth's largest extinction 251 million years ago at the Permian-Triassic Boundary. Ninety percent of the planet's marine life was destroyed and a great deal on land as well. Related sites: Garden of the Gods, Red Rocks Park, Roxborough State Park
Morrison Formation
The Morrison Formation was formed during the Cretaceous and Jurassic Period 100-150 million years ago. The Morrison Formation contains some of the best fossils of the Late Jurassic. It is especially known for its sauropod tracks and sauropod bones among other dinosaur fossils. As identified by the fossil record, the environment was filled with various types of vegetation such as ferns and zamites. Related site: Dinosaur Ridge, the roadcut at the Interstate 70 Morrison exit
Dakota Sandstone
Dakota Sandstone, formed during the Cretaceous period 70 to 100 million years ago, was deposited 100 million years ago towards Colorado's eastern coast. It shows evidence of ferns, and dinosaur tracks. Sheets of ripple marks can be seen on some of the strata, confirming the shallow-sea environment. Related sites are: Dinosaur Ridge, Garden of the Gods, Roxborough State Park, Deer Creek Canyon Park, the roadcut at the Interstate 70 Morrison exit.
Pierre Shale
Pierre Shale was formed during the Paleogene and Cretaceous periods about 70 million years ago. The region was taken over by a deep sea, the Cretaceous Western Interior Seaway, and deposited mass amounts of shale over the area known as the Pierre Shale. Both the thick section of shale and the marine life fossils found (ammonites and skeletons of fish and such marine reptiles as mosasaurs, plesiosaurs, and extinct species of sea turtles, along with rare dinosaur and bird remains). Colorado eventually drained from being at the bottom of an ocean to land again, giving yield to another fossiliferous rock layer, the Denver Formation. At about 68 million years ago, the Front Range began to rise again due to the Laramide Orogeny in the west. Related sites are: Garden of the Gods, Fountain Creek Nature Center, Rooney Road near Dinosaur Ridge, Valmont Dike
Fox Hills Formation
Fox Hills Formation was formed during the Paleogene / Cretaceous periods. It is a marginal marine yellow sandstone with shale interbeds created with the receding Western Interior Seaway in Late Cretaceous time.
Laramie Formation Laramie Formation, formed during the Cretaceous periods, is a geologic formation of the Denver Basin that ranges from 400 to 500 feet on the western side of the basin and 200–300 feet thick on the eastern side. The formation can be divided into a lower unnamed member containing bedded sandstone, clay, and coal and an upper unnamed member composed predominately of 90 to 190 m of drab-colored mudstone, some sandstone, and thin coal beds.Eldridge, G.H., 1888, On some stratigraphical and structural features of the country about Denver, Colorado: Colorado. Scientific Society Proceedings, v. 3, pt. 1, p. 86 118.Shroba, R.R., and Carrara, P.E., 1996, Surficial geologic map of the Rocky Flats environmental technology site and vicinity, Jefferson and Boulder Counties, Colorado: U.S. Geological Survey Miscellaneous Investigations Series Map, I 2526.King, C. 1876. Report of the Geological Exploration of the Fortieth Parallel. U.S.Geographical and Geological Survey.
Denver Formation
Denver Formation, formed during the Paleogene / Cretaceous periods 55 million years, contains fossils and bones from dinosaurs like Tyrannosaurus rex and Triceratops. While the forests of vegetation, dinosaurs, and other organisms thrived, their reign would come to an end at the Cretaceous–Paleogene boundary (K–T boundary). In an instant, millions of species are obliterated from a meteor impact in Mexico's Yucatan Peninsula. While this extinction lead to the dinosaurs' and other organisms' demise, some life did prevail to repopulate the earth as it recovered from this tremendous disaster. The uplifted Front Range continued to constantly erode and, by 40 million years ago, the range was once again buried in its own rubble. Related sites are: Austin Bluffs Park, Green Mountain, Palmer Park, Pulpit Rock Park, South Table Mountain
Paleosol – Dawson Arkose
Dawson Arkose, formed during the Paleogene period 37-55 million years ago, is up to 20 foot thick, multi-colored layers of clay form in this prehistoric tropical forest. This layer, Paleosol, is a soil of fossils such as petrified wood. An uplift occurred on the Front Range that caused the Pikes Peak granite to become exposed and then erode on the surface, resulting in a white sandstone called Dawson Arkose. Related sites are: Castlewood Canyon State Park, Daniel's Park, Paint Mines Interpretive Park, Rock Park
Castle Rock rhyolite
Castle Rock rhyolite was formed during the Paleogene period 34-37 million years ago. 37 million years ago, a great volcanic eruption took place in the Collegiate Range and covered the landscape in molten hot ash that instantly torched and consumed everything across the landscape. An entire lush environment was capped in a matter of minutes with 20 feet of extremely resistant rock, rhyolite. Related sites are: Castlewood Canyon State Park, Molly Brown House Museum, Rocks Park and mesa tops between Castle Rock and Monument Hill
White River Formation
The White River Formation is found in the Northeastern corner of the Colorado, and was deposited between ~37.2 and ~30.8 Ma, encompassing parts of the late Eocene and early Oligocene. The formation is composed primarily of claystones, mudstones, and siltstones, within which a variety of fossil organisms, collectively referred to as the White River fauna, can be found. The fossil assemblage of the formation includes tortoises, alligators, predatory birds, Perissodactyls such as primitive horses and rhinoceroses, Entelodonts, Nimravids, rodents, Artiodactyls, and other mammals. The paleoenvironment of the formation has been interpreted as being composed of expansive savannah-woodlands and plains, occasionally interrupted by meandering rivers.
Castle Rock conglomerate
Castle Rock conglomerate was formed 16,000 – 34 million years ago. However, as seen before, life rebounds, and after a few million years mass floods cut through the rhyolite and eroded much of it as plants and animals began to recolonize the landscape. The mass flooding and erosion of the volcanic rock gave way to the Castle Rock Conglomerate that can be found in the Front Range. About 10 million years ago, the Front Range began to rise up again and the resistant granite in the heart of the mountains thrust upwards and stood tall, while the weaker sediments deposited above it eroded away. Related sites: Castlewood Canyon State Park, Rocks Park
Quaternary sediments