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Map showing publication footprint
  • Usage in publication:
    • Italian Mountain Intrusive Complex*
  • Modifications:
    • Named
    • Geochronologic dating
  • Dominant lithology:
    • Quartz diorite
    • Quartz monzonite
  • AAPG geologic province:
    • Piceance basin
Publication:

Cunningham, C.G., Jr., and Naeser, C.W., 1975, The Italian Mountain Intrusive Complex, west-central Colorado, IN Cohee, G.V., and Wright, W.B., Changes in stratigraphic nomenclature by the U.S. Geological Survey, 1974: U.S. Geological Survey Bulletin, 1405-A, p. A27-A28.


Summary:

Named for heterogeneous assemblage of cogenetic intrusive rocks exposed in vicinity of Italian Mountain, Gunnison Co., CO in Piceance basin. Type locality designated at north peak of Italian Mountain, 20 km (12 mi) northeast of Crested Butte, Gunnison Co., CO. Consists of simple and composite plutons which range in composition from quartz diorite to quartz monzonite, and dikes which range in composition from dacite to rhyodacite. The oldest plutonic rock is a quartz diorite pluton south of the north peak of Italian Mountain. Dated at 33.0 +/-1.8 m.y., or Oligocene, using fission-track dating method of zircons.

Source: GNU records (USGS DDS-6; Denver GNULEX).


Map showing publication footprint
  • Usage in publication:
    • Italian Mountain Intrusive Suite*
  • Modifications:
    • Mapped 1:50k (Gunnison Co, CO)
    • Revised
  • Dominant lithology:
    • Quartz diorite
    • Dacite
    • Granite
  • AAPG geologic province:
    • Piceance basin
Publication:

Fridrich, C.J., DeWitt, Ed, Bryant, Bruce, Richard, Steve, and Smith, R.P., 1998, Geologic map of the Collegiate Peaks Wilderness Area and the Grizzly Peak caldera, Sawatch Range, central Colorado: U.S. Geological Survey Miscellaneous Investigations Series Map, I-2565, 1 sheet, 29 p., scale 1:50,000


Summary:

Mapped as Oligocene intrusive suite (revised) in northern part of Gunnison Co, CO (Piceance basin). Mapped in area of Italian Mountain in southwestern part of study area. Rank term revised from intrusive complex to more appropriate intrusive suite to conform to 1983 Stratigraphic Code. Unit described as medium- to dark-gray, medium grained, equigranular quartz diorite to light-gray, fine-grained, porphyritic dacite to granite. Younger than felsic plutons and dikes of Winfield Peak and Middle Mountain unit (Eocene); older than intrusive rocks of the White Rock pluton unit (Oligocene).

Source: GNU records (USGS DDS-6; Denver GNULEX).


For more information, please contact Nancy Stamm, Geologic Names Committee Secretary.

Asterisk (*) indicates published by U.S. Geological Survey authors.

"No current usage" (†) implies that a name has been abandoned or has fallen into disuse. Former usage and, if known, replacement name given in parentheses ( ).

Slash (/) indicates name conflicts with nomenclatural guidelines (CSN, 1933; ACSN, 1961, 1970; NACSN, 1983, 2005, 2021). May be explained within brackets ([ ]).

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