A Geological Tour of Denver, Golden, and Colorado's Front Range

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The Lykins Formation

Eroding mudstone of the Lykins Formation near Red Rocks Park

Eroding red mudstone near Red Rocks Park, could be easily mistaken for Fountain Formation sandstone, were it not for the Lykins Formation geological sign.

By Jack Barkstrom

Shallow seas and red mud...

Around 254 (251) million years ago a salty sea began to advance over what was left of the Lyons sand dunes, turning the region along the Front Range into a shallow tidal flat.  Algae found the environment to their liking, although most other life forms did not.  Sea water normally contains large amounts of calcium and bicarbonate ions which, on combining, precipitate out as limestone sediment, a carbonate rock or carbonate.  Although some organisms, such as primitive algae and corals, secrete calcium carbonate for use in their structures or shells, others do not.  Some forms of blue-green algae grow in colonies of sticky algal mats which trap fine carbonate sediments.  As the algae grow around the trapped sediments a layered structure or mound called a stromatolite is formed. Iron-rich clay and silt would be deposited around the growing stromatolite mounds, forming a red mudstone.[1]

The limestone and mudstone now known as the Lykins Formation, like the red sandstone of the Fountain Formation, provides little in the way of fossil evidence of larger plants or animals, either because of the chemistry or because few animals or plants inhabited the tidal flats.

The Permian Period ended and the Triassic Period began 248.2 (245) million years ago. What is known as the Permian-Triassic or the Permo-Triassic extinction took place at this time. It is estimated that between 90 and 96 percent of all species died. One theory is that volcanic activity in Siberia released large amounts of sulfur, which poisoned the atmosphere and water. The blue-green algae growing in Colorado appear to have been unaffected, since the limestone of the Lykins Formation continued being deposited for another forty million years, until 210 or 208 million years ago.[2]

(1) Frank Press and Raymond Siever, "Earth, 4th ed.," W. H. Freeman and Company, (New York 1986), pp. 314-322;
Kirk R. Johnson and Robert G. Raynolds, "Ancient Denvers: Scenes from the Past 300 Million Years of the Colorado Front Range," Denver Museum of Nature & Science, (Denver 2003), p. 10.
(2) David E. Fastovsky and David B. Weishampel, "The Evolution and Extinction of the Dinosaurs," Cambridge University Press, (New York 1996), pp. 389-390;
Stanley Chernicoff and Donna Whitney, "Geology: An Introduction to Physical Geology, 3rd ed." Houghton Mifflin Company, (New York, NY 2002)
Johnson and Robert G. Raynolds, "Ancient Denvers," p. 10.
Harald Drewes and John Townrow, "Trailwalker's Guide to the Dinosaur Ridge, Red Rocks and Green Mountain Area, 2nd Edition" Friends of Dinosaur Ridge, (Morrison, CO 2005), p. 43.