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 Information Entries for Little Bear Peak

Geology (Little Bear Peak)



Title: Rock Types

Entered by: shredthegnar10

Added: 06/01/2010, Last Updated: 06/01/2010


Igneous intrusives: granite (lighter-colored rocks), diorite (darker-colored rocks seen on the ridge)
Age: Tertiary


Geology (Little Bear Peak)



Title: Geology of Little Bear Peak

Entered by: rockdoc53

Added: 10/19/2010, Last Updated: 10/19/2010

Sources: Johnson, B.R. and Bruce, R.M., 1991, Reconnaissance geologic map of parts of the Twin Peaks and Blanca Peak Quadrangles, Alamosa, Costilla, and Huerfano counties, Colorado: U.S. Geological Survey Miscellaneous Field Studies Map MF-2169

Blanca, Ellingwood and Little Bear peaks are part of a granitic batholith formed over 1.7 billion years ago (Early Proterozoic). Little Bear Peak is composed predominantly of metagabbro. Metagabbro is a dark gray to very dark green, metamorphosed igneous rock of gabbroic composition, typically with phenocrysts of hornblende and plagioclase. A number of Miocene-Oligocene felsic dikes intrude the metagabbro on the western ridge. A glacier formed the U-shaped valley and a series of tarns, Lake Como, Blue Lakes and Crater Lake, that reside in the valley west of the Blanca-Ellingwood cirque. Similarly, a glacier formed the U-shaped valley and Little Bear Lake, west of the Little Bear Peak.

Geology (Sangre de Cristo)



Title: Stratigraphy and Paleogeography of the Northern Sangre de Cristo 14ers

Entered by: shredthegnar10

Added: 05/10/2010, Last Updated: 05/10/2010

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 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

Crestone Peak, Crestone Needle, Kit Carson Peak, Challenger Peak, and Humboldt Peak all include rocks of the Pennsylvanian (323-299 million years ago) Minturn Formation and the Pennsylvanian-Permian (306-251 million years ago) Sangre de Cristo Formation.
The Sangre de Cristo Formation gradationally overlies the Minturn Formation (meaning that there is no missing time between them), and is defined by the redbeds near the basal part of the Sangre de Cristo Formation. The Minturn Formation consists largely of marine sediments (limestones, siltstones, shales), whereas the Sangre de Cristo Formation consists of primarily nonmarine sediments (arkosic conglomerates, sandstones, siltstones). The shift in the depositional environment resulting in these differences is interpreted as the result of a large-scale sea level regression that occurred during the Middle Pennsylvanian.
The Sangre de Cristo Formation consists of two members (members are kind of like subdivisions of a geologic formation): the Crestone Conglomerate and the Lower Member. The Crestone Conglomerate is defined by the presence of cobble(64-256mm diameter) and boulder (>256mm diameter) sized clasts.
Both the Sangre de Cristo Formation and the Minturn Formation formations were deposited in a sedimentary basin known as the Central Colorado Trough, which was created as a result of the uplift of the Ancestral Rocky Mountains, an indirect result of continental collisions involved in the formation of the supercontinent Pangea. Drainage systems developed to transport eroded material off of these mountains into the basin, and that material is what makes up these formations.
In the limestones of the Minturn Formation, scientists have identified numerous fossils, including fusulinids, brachiopods, crinoids, and bryozoans.
FUN FACT: The sediments of the Sangre de Cristo Formation were deposited during the same time period as the rocks of the Maroon Formation, which make up the Maroon Bells and Pyramid Peak.


Name History (Little Bear Peak)



Title: Naming of Little Bear Peak

Entered by: 14erFred

Added: 05/14/2010, Last Updated: 05/14/2010

Sources: Hart, J.L.J. (1977). Fourteen thousand feet: A history of the naming and early ascents of the high Colorado peaks (Second Edition). Denver, CO: The Colorado Mountain Club.

Until 1916, Little Bear was known as "West Peak," because of its location just west of Blanca Peak. The mountain's official name was taken from a creek and lake on its west slopes.
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