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Northfield Formation

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Dark-gray to silvery-gray, lustrous, fine-grained carbonaceous quartz-muscovite phyllite and silicic phyllite, and garnet-rich biotite-muscovite-quartz schist; contains millimeter- to centimeter-thick beds of gray quartzite and metasiltstone, and thicker beds of quartz-feldspar grit or quartzite near base. Transition zone into Waits River Formation west of the Guilford dome consists of as much as 5 percent beds of punky limestone. Part of the Connecticut Valley Trough.
State Vermont
Name Northfield Formation
Geologic age Lower Devonian and Upper Silurian
Lithologic constituents
Major
Metamorphic > Metasedimentary > Metaclastic > PhylliteDark-gray to silvery-gray, lustrous, fine-grained carbonaceous quartz-muscovite phyllite and silicic phyllite.
Metamorphic > Schist > Mica-schistGarnet-rich biotite-muscovite-quartz schist.
Minor
Metamorphic > Metasedimentary > Metaclastic > MetasiltstoneContains millimeter- to centimeter-thick beds of gray quartzite and metasiltstone, and thicker beds of quartz-feldspar grit or quartzite near base.
Metamorphic > Metasedimentary > Metaclastic > QuartziteContains millimeter- to centimeter-thick beds of gray quartzite and metasiltstone, and thicker beds of quartz-feldspar grit or quartzite near base.
Comments On the printed map the unit label is DSn, but in the GIS it is Sn. Changing to DSn to match the printed map; Sn is a mistake according to Greg Walsh (oral communication 2012).
References

Ratcliffe, N.M., Stanley, R.S., Gale., M.H., Thompson, P.J., and Walsh, G.J., 2011, Bedrock geologic map of Vermont: U.S. Geological Survey Scientific Investigations Map 3184, 3 sheets, scale 1:100,000.

https://pubs.er.usgs.gov/publication/sim3184
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Counties Caledonia - Orange - Orleans - Washington - Windham - Windsor