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Fountain Formation

Physical Geology
Fall 2008


                          The Fountain Formation, Colorado



Pictured above are the Flatirons, Boulder, Colorado

            The Fountain Formation was named after Fountain, Colorado where an example of the Formation can be found. It is part of the Ancestral Rockies, or more commonly known as the Rocky Mountains.  Examples of the formation are known for their large, flat, reddish colored slabs of rock sticking out of the ground.  The Fountain Formation is mostly made of arkose.  Arkose is a type of intermediate sandstone, in which twenty-five percent or more is made of feldspar.  It is because of the high concentration of arkose and the oxidation of iron in the minerals, or rust, that they get their reddish pink color.


Pictured above is a close-up of arkose. [R.Weller/Cochise College]


The Making of the Fountain Formation:


            The Ancestral Rocky Mountains, which contains the Fountain Formation, was created about three hundred million years ago, during the early part of the Pennsylvanian Period.  During this period two ranges were created in the Mid-western United States, known as the Ancestral Rocky Mountains, or more commonly known as the Rocky Mountains. 


The above diagram explains the theory of how a subduction zone works [R.Weller/Cochise College]




            The Rockies were created as a result of a subduction zone process.  What makes the Rockies different from other mountain ranges created within a subduction zone is the angle at which the continental plate was subducted.  Normally the angle is steep, but in the case of the Rockies it was fairly flat, causing the mountains to form much further inland than they would in normal subduction cases.    When the continental plate is subducted at a steeper angle the mountains will form closer to where the two continental plates meet and the shore line.


United States of America before the Rocky Mountains.


During the subduction process, the waters receded as the Rocky Mountains formed.  The pink sandstone, arkose, was left as sediment from the area that was once the bottom of the Western Interior and Hudson Seaways.  The sandstone rose in sheets as the Rocky Mountains were formed.  Over tens of thousands of years, the Rocky Mountains have eroded and loose sediments on the mountains have washed away.  This has resulted in the large slabs of arkose becoming uncovered and prominently displayed.  The arkose slabs, in the Fountain Formation, are usually at angles which are somewhere between sixty and ninety degrees.


Pictured above is Roxborough State Park in Littleton, Colorado


Location and Examples:


Examples of the Fountain Formation can be found along the east side of the Front Range of the Rocky Mountains throughout the state of Colorado.  Some of the most well known examples of Fountain Formations are the Flatirons (Boulder, CO), Roxborough State Park (Littleton, CO), Garden of the Gods (Colorado Springs, CO), and Red Rocks Park and Amphitheater (Morrison, CO).


One of the most well known examples of the Fountain Formation is the Red Rocks Park and Amphitheater.  Situated just 15 miles west of Denver, Red Rocks is a geologically formed, open-air Amphitheatre.  Once listed as one of the Seven Wonders of the World,   Red Rocks has two main protrusions, Ship Rock and Creation Rock, both of which are taller than Niagara Falls.

Pictured above is a view of Red Rocks Amphitheater with Ship Rock outside Denver, Colorado


Many of the Fountain Formations have become tourist or recreational sites.  Roxborough State Park in Littleton, Colorado and the Garden of the Gods outside Colorado Springs, Colorado both offer recreational services such as hiking and camping.


Pictured above is The Garden of the Gods in Colorado Springs, Colorado



Pictured above is Roxborough State Park in Littleton, Colorado


            The Flatirons have become a symbol of Boulder, Colorado, where they are found.  There are five main formations, named in order Flatirons one through five.   Many businesses, including the city government of Boulder, Colorado and the University of Colorado use the Flatirons as their symbol.


Above is a Picture of the Flatirons taken from Boulder High School