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  • Usage in publication:
    • Berthelet member
  • Modifications:
    • Named
  • Dominant lithology:
    • Dolomite
  • AAPG geologic province:
    • Wisconsin arch
Publication:

Raasch, G.O., 1935, Devonian of Wisconsin, IN Kay, G.F., and Trowbridge, A.C., Conference leaders, Upper Mississippi Valley, Iowa City, Iowa, to Duluth, Minnesota: Kansas Geological Society Guidebook for the Annual Field Conference, August 25-September 1, 1935, no. 9, p. 261-267., Prepared in cooperation with Iowa, Illinois, Wisconsin, and Minnesota geol. surveys


Summary:

Named the Berthelet member as the basal member of the Milwaukee formation. Consists of dolomite and waterlime, dull gray, shaly in lower part, with upper few feet being a hard vitreous single layer of dolomite with many cavities containing calcite, marcasite, sphalerite, and millerite crystals, and asphaltum. Faunules change considerably vertically. Higher beds contain many cephalopods; below this, pelecypods and small brachiopods are abundant; lower beds have yielded mostly fish remains for which Milwaukee locality has long been famous. Thickness of the Berthelet member is 21 feet at the type locality. It underlies the Lindwurm member of the Milwaukee formation and overlies the Thiensville formation. Unit is of Middle Devonian 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 conflicts with nomenclatural guidelines (CSN, 1933; ACSN, 1961, 1970; NACSN, 1983, 2005, 2021). May be explained within brackets ([ ]).

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