Dakota Hogback; origins of Lyons sandstone formation

DAKOTA HOGBACK and LYONS SANDSTONE HOGBACK. The hogback can be seen west of the towns of Loveland and Lyons, between the open plains and the Rocky Mountains, with two highways cutting through the ridge. A cut through the hogback west of Denver on Interstate 70 reveals the various layers.

The Dakota Hogback is a long hogback ridge at the eastern fringe of the Rocky Mountains that extends north-south from southern Wyoming through Colorado and into northern New Mexico in the United States. The Lyons hogback starts near the Wyoming border and ends near the popular rock formations in Morrison and Colorado Springs, Colorado. The Dakota Ridge is usually called a Hogback because of its sharp top edge. The ridges are prominently visible as the first line of foothills along the edge of the Great Plains. It is generally faulted along its western side, and varies in height, with gaps in numerous locations where rivers exit the mountains. The ridge takes its name from the Dakota Formation, a sandstone formation that forms the ridge. The Lyons hogback is from the Lyons Formation.

The Dakota hogback was formed during the Laramide orogeny, approximately 50 million years ago, when the modern Rockies were created. The general uplift to the west created long faulting in the North American Plate, resulting in the creation of the hogbacks.[1]

While the Dakota hogback was created during the Laramide Orogeny, the geologic strata comprising the hogback are much older. For example, fossilized data such as dinosaur footprints have been observed in the exposed strata, created by dinosaurs which lived during the Jurassic Period approximately 150 my ago. Some of these footprints were attributed to the Diplodocus dinosaur and could be seen on the hogback west of Denver, Colorado as recently as the 1980s.[2]

The ridge forms a barrier between the high plains and the Rocky Mountain foothills. The ridge is pierced by a few water-cut gaps, which have been used to provide road access between the mountains and the plains. The ridge is paralleled by I-25 from north of Cheyenne, Wyoming, through Colorado, into northern New Mexico. The ridge is to the west. North of Denver its major gaps are; I-80 in southern Wyoming, U.S. Highways 34 at Loveland, U.S. 36 to Rocky Mountain National Park.[3] Interstate 70 passes through a highway cut, revealing the numerous layers making up the ridge. South of Denver, the major gaps are U.S. Route 24 in Colorado Springs, U.S. Route 50 in Pueblo, and finally in Colorado, U.S. Route 160 in Walsenburg.

Specifically in the Lyons area, and found in its quarry yards, one can find stone from the Lykins Formation, Lyons Formation, and Fountain Formation, each having a different structure and color. Lyons Sandstone‘s geological layer was formed during the Paleozoic Era, Middle Permian Period about 250 million years ago. This layer is also referred to as the Lyons Formation. It is not part of the shallow sea that once occupied the Front Range, but rather it is the result of fine-grained quartz sand dunes compressed into sandstone. As early as 6,500 years ago, in the Archaic period, the sandstone was used by early American Indians for its practical flat sturdy layers of varying thickness, which we refer to as flagstone. Commercial quarrying began in the 1880s, initially for building material, and expanded to decorative use in the 1940s. The town of Lyons has active, highly productive quarries today.

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Lyons History Video Project has a DVD that walks the viewer through some of the oldest Lyons sandstone quarries, …includes a visit to a Lyons quarry by the Geology Curator at the Denver Museum of Nature & Science, with geology maps in hand, and explanations in easy to understand language …and a view from a plane of Lyons and its surrounding quarries, and travelling along the hogback, from Lyons to Carter Lake. Contact lyonshistory@yahoo.com for more information. Cost $10.00 DVD (plus postage; or a mutually agreed to pick up location in Lyons) ~ Also good for use in “home schooling” geology.

ARTICLE References:
1^ Dakota Group in Northern Front Range Foothills, Colorado; Karl M. Waage; A Shorter Contribution to General Geology, Geological Survey Professional Paper 274-B; A revised subdivision and terminology for the Dakota group and local details of its Stratigraphy; United States Government Printing Office, Washington: 1955
2^ Guidebook on the Geology, History, and Surface-Water Contamination and Remediation in the Area from Denver to Idaho Springs, Colorado; Edited K.C. Stewart and R.C. Severson; U.S. Geological Survey Circular 1097; United States Government Printing Office, Washington, D.C. 1994
3 —NATIONAL PARKS: https://www.nps.gov/romo/dakota_hogback.htm

See also Garden of the Gods page.

BOOK on “Lyons Sandstone Quarries” by Alfred C. Pace, in cooperation with Lyons History Video Project. The book tells the story of Lyons quarries and the men who worked and formed the town of Lyons, including many photographs, old and new, and some maps. Available at the Lyons Museum (303) 823-5925; or write lyonshistory@yahoo.com for more information. $14.95

“Roadside Geology of Colorado” by Felicie Williams and Halka Chronic
Colorado’s stunning geology can be seen and understood through color photographs and color geologic maps.
The cover art changes with each new edition. This is a series of books of geology across America.
It is great to keep in your car because much of Colorado’s geology has been uncovered due to the roads that cut through the mountains. Most references in the book don’t even require any hiking to see. You can find it at thrift shops and book stores online from $5 to $25.