The National Geologic Map Database is migrating to a new infrastructure. We apologize for any service disruptions during this process.

U.S. Geological Survey Home AASG Logo USGS HOME CONTACT USGS SEARCH USGS
National Geologic Map Database
Map showing publication footprint
  • Usage in publication:
    • Eagle River porphyry*
  • Modifications:
    • Overview
  • AAPG geologic province:
    • Eagle basin
Publication:

Tweto, Ogden, 1951, Form and structure of sills near Pando, Colorado: Geological Society of America Bulletin, v. 62, no. 5, p. 507-532.


Summary:

Is a quartz monzonite porphyry in Eagle basin composed of abundant phenocrysts of feldspars, quartz, and biotite in a gray or greenish crystalline matrix. Is later than Lincoln porphyry. Was formerly included in Lincoln porphyry. Assigned to early Tertiary.

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


Map showing publication footprint
  • Usage in publication:
    • Eagle River Porphyry*
  • Modifications:
    • Age modified
  • AAPG geologic province:
    • Eagle basin
Publication:

Tweto, Ogden, 1974, Geologic map and sections of the Holy Cross quadrangle, Eagle, Lake, Pitkin, and Summit Counties, Colorado: U.S. Geological Survey Miscellaneous Investigations Series Map, I-830, 2 sheets, scale 1:24,000


Summary:

Occurs principally as sills in area between East Fork of Eagle River and East Tennessee Creek, Eagle Co., CO in Eagle basin. Is assigned to Paleocene?.

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 ([ ]).

Accessibility FOIA Privacy Policies and Notices

USA Gov U.S. Department of the Interior | U.S. Geological Survey
Supported by the National Cooperative Geologic Mapping Program
Page Contact Information: Personnel
Page Last Modified: Thu 21 May 2026 05:43:32 PM MDT