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Geologic Unit: Hedwig
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Map showing publication footprint
  • Usage in publication:
    • Hedwig breccia member*
  • Modifications:
    • Named
  • Dominant lithology:
    • Breccia
  • AAPG geologic province:
    • Great Basin province
Publication:

Ferguson, H.G., 1924, Geology and ore deposits of the Manhattan district, Nevada: U.S. Geological Survey Bulletin, 723, 163 p., (incl. geologic map, scale 1:24,000) [http://ngmdb.usgs.gov/Prodesc/proddesc_20337.htm]


Summary:

Named for outcrops in vicinity of Hedwig claim, Manhattan district, southern Toquima Range, Nye Co, NV. Is oldest of 4 named members of Esmeralda formation. Consists of well-cemented breccia composed of small angular fragments of various underlying Paleozoic rocks; contains no volcanic material. Interpreted to be old talus slope. Thickness difficult to determine, but probably less than 100 ft. Underlies Round Rock member (new) of Esmeralda formation. Shown on geologic map of Manhattan district as probably late Miocene(?) age.

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


Map showing publication footprint
  • Usage in publication:
    • Hedwig Breccia*
  • Modifications:
    • Revised
  • AAPG geologic province:
    • Great Basin province
Publication:

Kleinhampl, F.J., and Ziony, J.I., 1985, Geology of northern Nye County, Nevada: Nevada Bureau of Mines and Geology Bulletin, no. 99A, 172 p., (incl. geologic map, scale 1:250,000)


Summary:

Hedwig Breccia, which is herein removed from the Esmeralda Formation, is shown separately in Toquima Range on map of northern Nye Co, NV. Age given as Tertiary although "many clasts are of pre-Tertiary rocks".

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


Map showing publication footprint
  • Usage in publication:
    • Hedwig Breccia Member†
  • Modifications:
    • Abandoned
  • AAPG geologic province:
    • Great Basin province
Publication:

Shawe, D.R., 1987, Stratigraphic nomenclature of volcanic rocks near Manhattan, southern Toquima Range, Nye County, Nevada, IN Stratigraphic notes, 1985-86: U.S. Geological Survey Bulletin, 1775-A, p. A1-A8.


Summary:

Name Hedwig Breccia Member (Esmeralda Formation) of Ferguson (1924) abandoned. Unit is not separate talus breccia underlying Round Rock Member as interpreted by Ferguson (1924); contains significant exposed tuff identical to ash-flow tuff of lower member of Round Rock Formation and is intercalated with intracaldera facies rocks of the lower member about 1 km north of Manhattan. Rocks are renamed megabreccia unit of Sloppy Gulch and assigned to lower member of Round Rock Formation of late Oligocene age. Also contains volcanic clasts (up to 100 m long) embedded in tuff matrix not described by Ferguson (1924).

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


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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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