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Map showing publication footprint
  • Usage in publication:
    • Rochford Formation*
  • Modifications:
    • Named
  • Dominant lithology:
    • Chert
  • AAPG geologic province:
    • Midcontinent region
Publication:

Bayley, R.W., 1972, A preliminary report on the geology and gold deposits of the Rochford district, Black Hills, South Dakota, IN Contributions to economic geology: U.S. Geological Survey Bulletin, 1332-A, p. A1-A24, (incl. geologic map, scale 1:24,000) [http://ngmdb.usgs.gov/Prodesc/proddesc_21440.htm]


Summary:

Named as top formation of Flag Rock Group (rank raised) for exposures in the vicinity of Rochford, Pennington Co, SD in the Midcontinent region. Type locality is in secs 23 and 24, T2N, R3W. Overlies Nahant Schist (new) of Flag Rock Group. Underlies Poverty Gulch Slate (new). Composed of thick- to thin-bedded ferruginous chert and interlayers of silicate minerals, usually rosettes of grunerite, chlorite, mica and garnet. Composition varies locally. Is similar lithologically to basal formation of Flag Rock, the Montana Mine Formation (new). Thickness not stated. Very generalized description of lithology. Areal extent beyond report boundaries not discussed. Formerly mapped as unnamed part of Flag Rock Formation. Of middle Precambrian age. Geologic map.

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


Map showing publication footprint
  • Usage in publication:
    • Rochford Formation*
  • Modifications:
    • Age modified
  • AAPG geologic province:
    • Midcontinent region
Publication:

DeWitt, Ed, Redden, J.A., Wilson, A.E., and Buscher, David, 1986, Mineral resource potential and geology of the Black Hills National Forest, South Dakota and Wyoming, with a section on salable commodities by J.S. Dersch: U.S. Geological Survey Bulletin, 1580, 135 p., (incl. geologic map, scale 1:250,000)


Summary:

Mapped with Early Proterozoic unit Xif (Pl. 1) in the Rochford area, Pennington Co, SD in the Midcontinent region. Geologic map.

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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