Oldest gneiss complex

Chiefly layered granitic gneiss, locally migmatitic. Local masses of quartzite, metagraywacke, iron-formation, and other metasedimentary rocks and amphibolite and felsic gneiss thought to be volcanic; metasedimentary rocks in Beartooth Mountains contain detrital zircon dated at more than 3,400 Ma. Inclusions show evidence of granulite-facies metamorphism prior to 2,800 Ma. Mueller and others (1982) suggest that large areas in Beartooth Mountains were invaded by Late Archean granite (age about 2,800 Ma). Bighorn Mountains--Dates of metamorphism 3,000+ Ma.
State Wyoming
Name Oldest gneiss complex
Geologic age Early Archean
Lithologic constituents
Metamorphic > Gneiss
Metamorphic > Migmatite
Metamorphic > Amphibolite
Sedimentary > Chemical > Banded-iron-formation
Metamorphic > Metasedimentary > Metaclastic > Metasandstone > Metagraywacke
Metamorphic > Metasedimentary > Metaclastic > Quartzite
NGMDB product
Counties Big Horn - Fremont - Hot Springs - Johnson - Natrona - Park - Sublette - Washakie