Morrison Roadcut on I-70, North Side (Westbound) by Ron Schott

Canon EOS 550D (T2i)

GigaPan Epic100 (2nd generatio...

A Point of Geological Interest, as the highway signs describe it, just hints at the geological lessons that are laid bare here. The roadcuts that were exposed where Interstate 70 traverses the Dakota Hogback, just before rising out of Denver's western suburbs and rising into the Front Range proper, are a showcase of Mesozoic sedimentology and Cenozoic tectonics. At the west end (left) of the image is the aptly named T. rex parking lot (park & ride), with the Precambrian basement rocks of the Rocky Mountain Front Range supporting the hills on the horizon. The Jurassic Morrison Formation, just a few miles north of its type locality, is composed here of terrestrial fluvial deposits, mostly variegated shales and siltstones that can be seen near the center of this GigaPan. Further to the east (right) and stratigraphically upsection are Cretaceous sandstones of a number of formations, most notably the Dakota Sandstone which forms the backbone of this ridge and crops out naturally near its peak. The valley at the far east end (right) of this GigaPan is formed where the thick Mancos Shale has been more rapidly weathered and eroded away. The entire package of Mesozoic sedimentary rocks stands almost vertically today as a result of the uplift of the Rocky Mountain Front Range along a high angle reverse fault that runs along the base of the hills at the left (just behind the cement plant on the left side of the image) that was active during Latest Cretaceous and Paleogene times.