National Geologic Map Database
Geologic Unit: Wauseca
Search archives
Map showing publication footprint
  • Usage in publication:
    • Wauseca pyritic member*
  • Modifications:
    • Named
  • Dominant lithology:
    • Iron-formation
    • Slate
    • Breccia
  • AAPG geologic province:
    • Lake Superior region

James, H.L., 1958, Stratigraphy of pre-Keweenawan rocks in parts of northern Michigan, IN Shorter contributions to general geology, 1957: U.S. Geological Survey Professional Paper, 314-C, p. C27-C44. [Available online from the USGS PubsWarehouse: http://pubs.er.usgs.gov/pubs/pp/pp314C]


Named for exposures at the Wauseca mine at Iron River, southern Iron Co, northwest MI in the Lake Superior region, where unit is exposed in thousands of ft of mine workings. Is exposed at roadcut south of town of Alpha and known from test pits, mine workings, and drillholes throughout district. Is a member of Dunn Creek slate (new) and forms the uppermost part immediately below Riverton iron-formation (new). Is generally a black, deformed, pyritic, graphitic slate probably 30 ft or less in thickness. Contains 35 to 40 percent pyrite and 5 to 10 percent free carbon. Subdivided into 2 or 3 units where mapped in mines. One subunit is a variably thick, chaotic breccia consisting of inch-or-less-size fragments of pyritic slate in a similar pyritic matrix. Is believed to be a product of submarine slumping. Is middle Precambrian in age.

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