GEOLEX

Summary of Citation: Buffalo Peaks

Publication:
Gould, D.B., 1935, Stratigraphy and structure of Pennsylvanian
   and Permian rocks in Salt Creek area, Mosquito Range, Colorado:
   American Association of Petroleum Geologists Bulletin, v.
   19, no. 7, p. 971-1009

Usage in Publication:
Buffalo Peaks andesite

Modifications:	Geologic Province:	Dominant Lithology:
First used	South Park basin	Andesite

Summary:
First published use for an andesite near Buffalo Peaks, T12S, R77W, Park Co, CO, South Park basin. Intent to name not stated. No type locality designated. Is a Tertiary unit that covers the newly named Pony Spring siltstone member of Maroon formation in the northwest part of Salt Creek area, Park Co, CO in the South Park basin. A Tertiary erosion surface was produced at top of Pony Spring before extrusion of Buffalo Peaks.

Summary of Citation: Buffalo Peaks

Publication:
Stark, J.T., Johnson, J.H., Behre, C.H., Jr., Powers, W.E.,
   Howland, A.L. and Gould, D.B., 1949, Geology and origin of
   South Park, Colorado: Geological Society of America Memoir,
   33, 188 p.

Usage in Publication:
Buffalo Peaks andesite

Modifications:	Geologic Province:	Dominant Lithology:
Overview	South Park basin	Andesite

Summary:
Andesite that differs from other andesites in the South Park area, present at Buffalo Peaks and at Hall Butte west of Antero junction, and near the McQuaid Ranch designated Buffalo Peaks andesite. Intent to name and designation of type locality not stated. Is 500 to 600 ft thick at west end of West Hall Butte and 200 to 300 ft at east end of Butte. Is a gray to black andesite with hornblende and pyroxene phenocrysts. Flow structure and platy jointing common. Cannot be dated accurately. Early Oligocene age suggested. Is older than an unnamed Tertiary trachyte. Is younger than Thirtynine Mile andesite (new). Geologic map.

Summary of Citation: Buffalo Peaks

Publication:
Sanders, G.F., Jr., Scott, G.R. and Naeser, C.W., 1976, The
   Buffalo Peaks Andesite of central Colorado, IN Contributions
   to stratigraphy: U.S. Geological Survey Bulletin, 1405-F, p.
   F1-F8

Usage in Publication:
Buffalo Peaks Andesite*

Modifications:	Geologic Province:	Dominant Lithology:
Overview Age modified	South Park basin Eagle basin

Summary:
Is a light- to dark-gray or brownish-gray, porphyritic andesite with phenocrysts of plagioclase, hornblende, and pyroxene. Hornblende phenocrysts are prominent; some are as much as 2 cm long. Lower part is a reddish-brown breccia that contains fragments of moderately welded red and underlying ash-flow tuff; the contact between breccia and underlying tuff is disconformable. The top of the andesite is eroded. Is 565 ft (172 m) thick at Buffalo Peaks. The Oligocene? age is determined from its stratigraphic position above the Wall Mountain Tuff (considered early Oligocene age in earlier reports). Is preserved as erosional remnants at East and West Hall Buttes, and East Buffalo Peak in Park Co, and at West Buffalo Peak in Park and Chaffee Cos, CO in South Park, South Park and Eagle basins.

Summary of Citation: Buffalo Peaks

Publication:
Marvin, R.F. and Mehnert, H.H., 1988, Radiometric ages; compilation
   "C", U.S. Geological Survey; Part two, Arizona and New Mexico:
   Isochron/West, no. 51, p. 5-13

Usage in Publication:
Buffalo Peaks Andesite*

Modifications:	Geologic Province:	Dominant Lithology:
Isotopic dating	Eagle basin

Summary:
Sample from NE1/4 NE1/4 sec 22, T14S, R77W, Antero Reservoir 15 min quad, Chaffee Co, CO in Eagle basin, dated isotopically. Sample is from an andesitic ash-flow tuff (Badger Creek Tuff) which is overlain by Buffalo Peaks Andesite and underlain by Wall Mountain Tuff. Biotite yielded K-Ar date of 36.3 +/-0.9 Ma; hornblende yielded 37.4 +/-0.7 Ma.