Explore Map Collection

Check out our basemaps

Print a Map Plus

Generate a high-quality PDF

Discover local flora, fauna, geology, and more

Local Flora & Fauna

Learn the ecology of your area

Learn the geologic formation at your feet

Get Started or Sign In

Welcome

Sign up to start exploring the one-of-a-kind Natural Atlas Topo map

Continue with Apple

Or

Already have an account? Sign In

MAP

Topo

Rock Formations

Measure

Copyright © Natural Atlas | Roads, Buildings © OSM Contributors | Data Sources

Topo

Ecoregions

Public Lands

...

BASEMAPS

Default Weather

Temperature

Smoke

...

WEATHER

Oldest gneiss complex (WYUgn;0)

Geologic Formation in WY, MT

Generate High-Quality PDF

Lithology

Gneiss

Migmatite

Amphibolite

Other (1,120 mi²)

Geologic Age

Precambrian Archean (4000 Ma – 2500 Ma ago)

Geologic Unit Label

Ugn

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.

— USGS

Taxonomy

Classified As

Geologic Formation