27 June 2013
At Morton Pass, where highway 34 crosses the crest of the Laramie Range, you can see a nice set of (younger) mafic dikes cutting (older) granite/gneiss basement complex. The pink stuff is Archean; the black stuff is Paleoproterozoic; around 2 billion years old.
I got to check out this outcrop on Tuesday with colleagues from the University of Missouri and the University of Wyoming. Deformation in the dikes helps constrain the tectonic history of this parcel of ancient rock.