Road Trip To The Boundary Waters (32)
The Bighorns (Part 2)
Note: This is a continuation of Part 1, the drive up the Scenic Byway, Highway 16 in the southern Bighorn Mountains.
There is an almost two billion year gap of missing rock formations between the Bighorn dolomite—described in the previous post— and this igneous rock exposure, which is older than any rocks in the Grand Canyon.
The oldest rocks in the Bighorns, and some of the oldest rocks in the world, occur at the highest elevations. Three billion years is a minimum age for these rocks, which can be up to 3.5 billion years old, comparable to the Morton Gneiss in Minnesota.
A gneiss is a highly metamorphosed rock, in this case granite. On the left a closeup; on the right, the peak, consisting entirely of 3+ billion year old rocks.
This is not a gneiss. I don’t know what it is. but the lichen decorations are beautiful.
