Geology (Mt. Lindsey)
Title: Mt. Lindsey Geology
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,Little Bear and Mt. Lindsey are part of a granitic batholith formed over 1.7 billion years ago (Early Proterozoic). The top of Mt. Lindsey is the upper plate of a thrust composed predominantly of Early Proterozoic tonalite gneiss and metagabbro with a few Proterozoic mafic dikes intruding the tonalite gneiss. Metagabbro is a dark gray to very dark green, metamorphosed igneous rock of gabbroic composition, typically with phenocrysts of hornblende and plagioclase. Tonalite gneiss is a white to light gray green metamorphosed igneous rock of tonalite composition, typically 60% plagioclase, 30% quartz 2% potassium feldspar, and 8% percent mafic minerals altered to epidote, chlorite and muscovite. The lower plate, exposed on the north side of Lindsey is composed of Early Proterozoic hornblende gneiss.
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.