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National Geologic Map Database
Geologic Unit: Lake Fork
Map showing publication footprint
  • Usage in publication:
    • Lake Fork andesite*
  • Modifications:
    • Redefined
  • Dominant lithology:
    • Andesite
    • Breccia
  • AAPG geologic province:
    • Piceance basin
Publication:

Map showing publication footprint
  • Usage in publication:
    • Lake Fork Formation*
  • Modifications:
    • Age modified
    • Redescribed
  • AAPG geologic province:
    • Piceance basin
Publication:

Olson, J.C., Hedlund, D.C., and Hansen, W.R., 1968, Tertiary volcanic stratigraphy in the Powderhorn-Black Canyon region, Gunnison and Montrose Counties, Colorado, IN Contributions to general geology, 1967: U.S. Geological Survey Bulletin, 1251-C, p. C1-C29.


Summary:

Redescribed from Lake Fork Quartz Latite to Lake Fork Formation because formation contains a heterogeneous assemblage of units (gravel and andesitic flows, breccia and pyroclastic rocks, rhyodacitic lava, tuff) rather than quartz latite. Ranges from 0 to 1,600 ft in Gateview quad; thickens to about 4,000 ft 5 mi south of Gateview. Age changed from Miocene to Oligocene and older. Used near Lake Fork of the Gunnison River in Piceance basin. Formed at same time as Conejos Quartz Latite in San Luis basin, and as the West Elk Breccia of the West Elk area of Piceance basin.

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


Map showing publication footprint
  • Usage in publication:
    • Lake Fork Formation*
  • Modifications:
    • Geochronologic dating
  • AAPG geologic province:
    • San Juan Mountains province
Publication:

Lipman, P.W., Steven, T.A., Luedke, R.G., and Burbank, W.S., 1973, Revised volcanic history of the San Juan, Uncompahgre, Silverton, and Lake City calderas in the western San Juan Mountains, Colorado: U.S. Geological Survey Journal of Research, v. 1, no. 6, p. 627-642.


Summary:

Interfingers with mudflow breccias of San Juan Formation. Shown as an early Oligocene unit equivalent to Picayune Formation (also a vent facies). A lava flow in the Lake Fork has a 31.4 m.y. age.

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 does not conform with nomenclatural guidelines (CSN, 1933; ACSN, 1961, 1970; NACSN, 1983, 2005). This may be explained within brackets ([ ]).