Piegan Group. (IDYpi;0)

Piegan Group.

Calcareous and dolomitic siltite, quartzite, and subordinate argillite of the Helena and Wallace formations in northern Idaho; south of St. Joe River, correlative rocks include garnet grade feldspathic quartzite and calc-silicate gneiss. (Mesoproterozoic Belt Supergroup).

State	Idaho
Name	Piegan Group.
Geologic age	Mesoproterozoic
Lithologic constituents	Major Metamorphic > Metasedimentary > Metaclastic > MetasiltstoneCalcareous and dolomitic siltite. Metamorphic > Metasedimentary > Metaclastic > QuartziteQuartzite and garnet grade feldspathic quartzite. Minor Metamorphic > Gneiss > Calc-silicate-gneiss Metamorphic > Metasedimentary > Metaclastic > Argillite
References	Lewis, Reed S., Link, Paul K., Stanford, Loudon R., and Long, Sean P., Geologic Map of Idaho, 2012, Idaho Geological Survey, Geologic Map 9 (M-9); Scale 1:500,000.
NGMDB product	NGMDB product page for 97750
Counties	Benewah - Bonner - Boundary - Clearwater - Idaho - Kootenai - Latah - Shoshone

Piegan Group.

Lewis, Reed S., Link, Paul K., Stanford, Loudon R., and Long, Sean P., Geologic Map of Idaho, 2012, Idaho Geological Survey, Geologic Map 9 (M-9); Scale 1:500,000.