|Challenger Point Group|
Geology (Challenger Point)
Title: Geologic History of the Crestones
Entered by: ztop
Added: 06/30/2010, Last Updated: 06/30/2010
Sources: Bolyard, D.W., 1959, Pennsylvanian and Permian stratigraphy of the Sangre de Cristo Mountains between La Veta Pass and Westcliffe, Colorado: American Association of Petroleum Geologists Bulletin, v. 43, p. 1896-1939 Blakey, Ron, 2005 (and updates online)http://jan.ucc.nau.edu/~rcb7/garm.html; Brill, K.G., 1952, Stratigraphy in the Permo-Pennsylvanian zeugogeosyncline of Colorado and northern New Mexico: Geological Society of America Bulletin, v. 63, p. 809-890 Hoy, R.G. and Ridgway, K.D., 2002, Syndepositional thrust-related deformation and sedimentation in an Ancestral Rocky Mountains basin, Central Colorado Trough, Colorado, USA: Geological Society of America Bulletin, v. 114, p.804-828 Lindsey, D.A., Clark, R.F., and Soulliere, S.J., 1986, Minturn and Sangre de Cristo formations of southern Colorado; a prograding fan delta and alluvial fan sequence shed from the Ancestral Rocky Mountains, American Association of Petroleum Geologists Memoir 41, p. 541-561
One of the most exciting times in Colorado geologic history was the Pennsylvanian period when continental collisions formed the Ancestral Rocky Mountains. Europe and Africa collided with North America forming the Appalachian and Ouachita Mountains, and North America tried to break in two through southern Oklahoma. As the continent was being squeezed and ripped apart, the Uncompahgre highland was uplifted in central and western Colorado, the Front Range and Apishapa uplifts to the east, and the Central Colorado Trough became a deep basin between the two highlands.
During the late Pennsylvanian and Permian periods, massive amounts of sediment were shed off the Uncompahgre into the trough. The coarsest sediments are called the Crestone conglomerate (see shredthegnar10's report). Boulders up to 10' in diameter rolled down the mountainsides and were deposited in a pile of sediment that reached more than 9000' in thickness, a massive amount of bouldery rock. It was an environment similar to that of Red Rocks and Garden of the Gods, but must have been much steeper with more dramatic landslides and mudflows. There is very little fine grained sediment, but one notable band is much-beloved by readers on this website. Kit Carson Avenue is a bench developed on a 4-6' thick mudstone which is amazingly continuous considering how little fine-grained sediment there is in the Crestones. There are still huge boulders in this mudstone, but its softness allows it to weather out and leave a path across Kit Carson Peak.
Ironically, the basin where those rocks were deposited has been inverted and now forms the spine of the Crestone Peaks area of the Sangre de Cristo Mountains. The cement that holds the boulders together makes the Crestone Conglomerate a stable and hard rock as many climbers appreciate.
The sediments form a 3000' high wall on these peaks, a massive amount of coarse-grained conglomerate to be deposited in narrow basin.