GEOLEX

Summary of Citation: Treasure Mountain

Publication:
Patton, H.B., 1917, Geology and ore deposits of the Platoro-Summitville
   mining district, Colorado: Colorado Geological Survey Bulletin,
   no. 13, 122 p.

Usage in Publication:
Treasure Mountain latite

Modifications:	Geologic Province:	Dominant Lithology:
First used	San Juan Mountain province San Luis basin	Latite

Summary:
First published use, but not used consistently in text. Term "biotite latite" applied in parts of text and to map unit Cross [no reference given] applied the name "Treasure Mountain formation." Biotite latite mapped (geologic map) in east and south part of area north of Conejos River, south of Alamosa River, and east of the Summitville andesite (named) outcrops, Rio Grande Co, CO, San Juan Mountain province, and Conejos Co, CO in the San Luis basin. The biotite latite described as gray to brown, fine textured, non-glassy groundmass, numerous minute inconspicuous phenocrysts of whitish feldspar and brown biotite. Breaks into slabs. Has many angular fragments of other igneous rocks. Has flow structure. Tertiary age. [Intent to name, describe or define as a formal name not stated.]

Summary of Citation: Treasure Mountain

Publication:
Cross, C.W. and Larsen, E.S., 1935, A brief review of the geology
   of the San Juan region of southwestern Colorado: U.S. Geological
   Survey Bulletin, 843, 138 p., Also, U.S. Geological Survey
   Professional Paper 258.

Usage in Publication:
Treasure Mountain quartz latite*

Modifications:	Geologic Province:	Dominant Lithology:
Redescribed	San Juan basin	Quartz latite

Summary:
Redescribed--name changed from Treasure Mountain latite to Treasure Mountain quartz latite. Is one of six formations assigned to the Miocene Potosi volcanic series. Occurs in CO in Archuleta Co in the San Juan basin, in Hinsdale and Mineral Cos in the San Juan Mountain province, and in Saguache, Rio Grande, and Conejos Cos in the San Juan basin. Is made up of alternating latite flows and tuffs. The thickest, most widespread flows are composed of biotite-augite-tridymite latite. Many of the flows are 100 +/-ft thick and maintain that thickness for miles. Is younger than the Conejos andesite (formerly called Conejos formation) and older than Sheep Mountain andesite. Geologic map.

Summary of Citation: Treasure Mountain

Publication:
Barker, Fred, 1958, Precambrian and Tertiary geology of Las
   Tablas quadrangle, New Mexico: New Mexico Bureau of Mines
   and Mineral Resources Bulletin, no. 45, 104 p.

Usage in Publication:
Treasure Mountain welded tuff

Modifications:	Geologic Province:	Dominant Lithology:
Redescribed	San Juan basin	Tuff

Summary:
Extends southward from CO into the upper Tusas Valley, Rio Arriba Co, NM in the San Juan basin. Redescribed--name changed from Treasure Mountain formation to Treasure Mountain welded tuff. The lower welded tuff is dark gray to black, mostly vitreous, in which both lithic and crystal fragments are faintly to markedly parallel to gross layering. The upper layer is pink to brick red or olive brown, dense, homogeneous, and fractures with a conchoidal pattern. Ranges from 10 to 100 ft thick. Is younger than the Conejos? formation and older than Biscara member of the Los Pinos formation. Assigned to the Miocene.

Summary of Citation: Treasure Mountain

Publication:
Lipman, P.W. and Steven, T.A., 1970, Reconnaissance geology and
   economic significance of the Platoro caldera, southeastern
   San Juan Mountains, Colorado, IN Geological Survey research
   1970: U.S. Geological Survey Professional Paper, 700-C, p.
   C19-C29

Usage in Publication:
Treasure Mountain Tuff*

Modifications:	Geologic Province:	Dominant Lithology:
Revised Redescribed	San Luis basin

Summary:
Renamed Treasure Mountain Tuff (formerly called Treasure Mountain Rhyolite). Redescribed to include only those units at Treasure Mountain plus additional intertonguing tuffs farther south. Three large ash-flow sheets mapped over nearly 5,000 km, which are formally named in this report. Divided in the San Luis basin into (ascending order): lower tuff, La Jara Canyon Member (new), middle tuff, Ojito Creek Member (new), and Ra Jadero Member (new). Unconformably overlies the Conejos Formation; unconformably underlies the tuff of Masonic Park. La Jara Canyon Member dated at 29.8 m.y. Assigned to the Oligocene.

Summary of Citation: Treasure Mountain

Publication:
Steven, T.A. and Lipman, P.W., 1976, Calderas of the San Juan
   volcanic field, southwestern Colorado: U.S. Geological Survey
   Professional Paper, 958, 35 p.

Usage in Publication:
Treasure Mountain Tuff*

Modifications:	Geologic Province:	Dominant Lithology:
Overview	San Luis basin San Juan basin San Juan Mountain province

Summary:
Areal limits of its three members--La Jara Canyon, Ojito Creek, and Ra Jadero--shown. Ash-flow activity began 30-29 m.y. ago when La Jara Canyon erupted from Platoro caldera. La Jara Canyon spread over Archuleta Co, CO in the San Juan basin, Conejos and Rio Grande Cos, Co in the San Luis basin, and Mineral Co, CO in the San Juan Mountain province. Caldera collapse began before eruptions were complete. The Summitville caldera occupies the northern part of Platoro caldera. Ojito Creek and Ra Jadero Members were erupted after the Platoro caldera moat was filled by lavas of the Summitville Andesite. Ojito Creek and Ra Jadero Members spread over same general area as the La Jara Canyon. Areal extent maps of members. Two quartz latite sheets thought to be derived from the Mount Hope caldera removed from top of Treasure Mountain and named Masonic Park Tuff. Ages of the three members range from less than 29.8 to greater than 29.1 m.y.

Summary of Citation: Treasure Mountain

Publication:
Lipman, P.W., Dungan, M.A., Brown, L.L. and Deino, Alan, 1996,
   Recurrent eruption and subsidence at the Platoro Caldera
   complex, southeastern San Juan volcanic field, Colorado; new
   tales from old tuffs: Geological Society of America Bulletin,
   v. 108, no. 8, p. 1039-1055

Usage in Publication:
Treasure Mountain Group*

Modifications:	Geologic Province:	Dominant Lithology:
Revised	San Juan Mountain province San Juan basin San Luis basin

Summary:
Raised to group rank and divided into eight units (ascending): lower rhyolite tuff, Black Mountain (new) and La Jara Canyon (rank raised) Tuffs, middle tuff, Ojito Creek (rank raised), Ra Jadero (rank raised), South Fork (new), and Chiquito Peak (new) Tuffs. Study area is within southeastern San Juan volcanic field, Archuleta (San Juan basin), Mineral (San Juan Mountain province), and Rio Grande and Conejos (San Luis basin) Cos, CO. Each of the major named tuffs raised to formation rank because they are as voluminous as some tuff sheets designated as formations elsewhere in San Juan field. Component units are ash-flow sheets erupted from multicyclic Platoro caldera complex during interval 29.5-28.4 Ma (Oligocene).