U.S. Geological Survey Home AASG Logo USGS HOME CONTACT USGS SEARCH USGS
National Geologic Map Database
Geologic Unit: Dunbar
Search archives
Map showing publication footprint
  • Usage in publication:
    • Dunbar Gneiss*
  • Modifications:
    • Named
  • Dominant lithology:
    • Gneiss
  • AAPG geologic province:
    • Lake Superior region
Publication:

Cain, J.A., 1964, Preliminary report on the Precambrian geology of the Athelstane area, northeastern Wisconsin: Ohio Journal of Science, v. 64, no. 1, p. 57-60.


Summary:

Named as formation, presumably for Dunbar, Marinette Co, WI, Lake Superior region. Type not designated. Geologic map (fig 1) shows areal extent. Is apparently part of "mafic quartz diorite" of Lyons (1947), unit he recognized as older than "normal quartz diorite." Consists of two types: medium- to coarse-grained banded gneiss and fine-grained migmatitic gneiss. Characteristic minerals of banded gneiss are plagioclase, quartz, biotite, microcline, apatite, and sphene. Characteristic minerals of migmatitic gneiss are sodic feldspar, quartz, biotite, epidote, apatite, sphene, and garnet. Relationship to Marinette Quartz Diorite and Twelve Foot Falls Quartz Diorite (new) not established due to lack of exposures. Quinnesec Formation and migmatitic gneiss may be penecontemporaneous and represent different lithologies within geosynclinal sequence of sedimentary, volcanic, and associated intrusive rocks (banded gneiss, Marinette Quartz Diorite, and Twelve Foot Falls Quartz Diorite). Probably pre-Animikie in age (Early Precambrian).

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


Map showing publication footprint
  • Usage in publication:
    • Dunbar Gneiss*
  • Modifications:
    • Geochronologic dating
  • AAPG geologic province:
    • Lake Superior region
Publication:

Sims, P.K., Peterman, Z.E., and Schulz, K.J., 1984, Dunbar gneiss-granitoid dome, IN Sims, P.K., and others, leaders, Guide to the geology of the Early Proterozoic rocks in northeastern Wisconsin; Field trip 1: Institute on Lake Superior Geology Field Trip, 30th annual meeting, p. 1-23.


Summary:

Average 87Rb/86Sr and 87Sr/86Sr values for 11 samples used to calculate model age of 1,875 +/-70 Ma. U-Pb zircon age for Dunbar Gneiss is 1,862 +/-5 Ma. Assigned to Early Proterozoic. Oldest unit of Dunbar dome, Lake Superior region.

Source: GNU records (USGS DDS-6; Reston 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 04 Apr 2024 03:18:44 PM MDT