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Geologic Units: Trommald
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Map showing publication footprint
  • Usage in publication:
    • Trommald Formation
  • Modifications:
    • Mapped 1:250k
  • Dominant lithology:
    • Iron-formation
  • AAPG geologic province:
    • Lake Superior region
Publication:

Southwick, D.L., Morey, G.B., and McSwiggen, P.L., 1988, Geologic map of the Penokean Orogen, central and eastern Minnesota: Minnesota Geological Survey Report of Investigations, no. 37, 25 p., (incl. geologic map, scale 1:250,000)


Summary:

Is mapped as middle formation (of 3) of the North Range Group (Early Proterozoic) in Crow Wing Co, central MN (Lake Superior region). Overlies Mahnomen Formation of North Range Group. Overlain by Rabbit Lake Formation of North Range Group. Map unit described as interlayered cherty and slaty iron-formation, moderately deformed and weakly metamorphosed. Thickness not given.

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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