Ellingwood Point Group

Geology (Ellingwood Point)



Title: Geology of Ellingwood Point

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

Ellingwood Point is composed predominantly of 1.7 billion year old (Early Proterozoic) metagabbro, which is is a dark gray to very dark green, metamorphosed igneous rock of gabbroic composition, typically with phenocrysts of hornblende and plagioclase. 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.

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.



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