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National Geologic Map Database
Geologic Unit: Shelton
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Map showing publication footprint
  • Usage in publication:
    • Shelton Member*
  • Modifications:
    • Named
  • Dominant lithology:
    • Gneiss
    • Schist
  • AAPG geologic province:
    • New England province
Publication:

Rodgers, John, 1985, Bedrock geological map of Connecticut: Connecticut Geological and Natural History Survey, scale 1:125,000


Summary:

Rocks mapped as the Shelton facies of the Trap Falls Formation by Crowley (1968) are here named the Shelton Member of the Trap Falls in the Hartland belt of the Connecticut Valley synclinorium. It consists of white, light-gray, or buff, fine- to medium-grained, foliated granitic gneiss composed of sodic plagioclase, quartz, microcline, muscovite, and garnet in tiny grains, interlayered with mica schist, biotite, gneiss, and calc-silicate rock. It is thought to be the metavolcanic equivalent of granitic gneiss which has been termed Ansonia, Mine Hill, "Tyler Lake," and "Siscowit" gneiss. Age is Early or Middle Ordovician.

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


Map showing publication footprint
  • Usage in publication:
    • Shelton muscovite granite
  • Modifications:
    • Redescribed
    • Revised
    • Geochronologic dating
    • Age modified
  • AAPG geologic province:
    • New England province
Publication:

Sevigny, J.H., and Hanson, G.N., 1993, Orogenic evolution of the New England Appalachians of southwestern Connecticut: Geological Society of America Bulletin, v. 105, no. 12, p. 1591-1605.


Summary:

Shelton Member of Trap Falls Formation (Rodgers, 1985) is here referred to as Shelton muscovite granite. On the basis of field and laboratory studies, Ansonia, Beardsley, Pumpkin Ground, and Shelton gneisses, previously considered stratigraphic units, are reinterpreted as plutonic. Shelton is a foliated, medium-grained, garnet-bearing muscovite leucogranite with a conspicuous white color and abundant garnets. Age of crystallization determined from U-Pb garnet analysis is 380+/-3 Ma (Middle Devonian). Southeast margin of the Shelton is in contact with the Trap Falls Formation.

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 ([ ]).