Ironbound Mountain Formation - Halls Stream Grit member (of Myers, 1964) (VTDih;0)

Ironbound Mountain Formation - Halls Stream Grit member (of Myers, 1964)

Lenticular masses of coarse-grained quartzose volcaniclastic grit and cobble metaconglomerate commonly with abundant dark-gray metapelitic matrix (diamictite) interlayered with metasandstone, metapelite, and porphyritic metarhyolite. Grit contains subangular clasts of plagioclase and potassic feldspar as large as 2.5 cm across and larger clasts of dark-gray slate. Conglomerate contains rounded clasts of metarhyolite, fine-grained granitoid, and rare marble, and angular clasts of dark-gray slate. Part of the Connecticut Valley Trough.

State	Vermont
Name	Ironbound Mountain Formation - Halls Stream Grit member (of Myers, 1964)
Geologic age	Lower Devonian
Lithologic constituents	Major Metamorphic > Metasedimentary > Metaclastic > MetaconglomerateCobble metaconglomerate commonly with abundant dark-gray metapelitic matrix (diamictite) interlayered with metasandstone, metapelite, and porphyritic metarhyolite. Conglomerate contains rounded clasts of metarhyolite, fine-grained granitoid, and rare marble, and angular clasts of dark-gray slate. Igneous > Volcanic > Felsic-volcanic (Volcaniclastic)Lenticular masses of coarse-grained quartzose volcaniclastic grit. Minor Metamorphic > Metasedimentary > Metaclastic > MetasandstoneCobble metaconglomerate commonly with abundant dark-gray metapelitic matrix (diamictite) interlayered with metasandstone, metapelite, and porphyritic metarhyolite. Metamorphic > Metaigneous > Metavolcanic > MetarhyoliteCobble metaconglomerate commonly with abundant dark-gray metapelitic matrix (diamictite) interlayered with metasandstone, metapelite, and porphyritic metarhyolite. Conglomerate contains rounded clasts of metarhyolite. Metamorphic > Metasedimentary > MetaclasticCobble metaconglomerate commonly with abundant dark-gray metapelitic matrix (diamictite) interlayered with metasandstone, metapelite, and porphyritic metarhyolite. Incidental Metamorphic > Metasedimentary > Metaclastic > SlateGrit contains subangular clasts of plagioclase and potassic feldspar as large as 2.5 cm across and larger clasts of dark-gray slate. Conglomerate contains rounded clasts of metarhyolite, fine-grained granitoid, and rare marble, and angular clasts of dark-gray slate. Metamorphic > Metasedimentary > Metacarbonate > MarbleConglomerate contains rounded clasts of metarhyolite, fine-grained granitoid, and rare marble, and angular clasts of dark-gray slate.
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
NGMDB product	NGMDB product page for 96860
Counties	Essex

Ironbound Mountain Formation - Halls Stream Grit member (of Myers, 1964)

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.