GRAND TETONS NATIONAL PARK
(photos from the textbook CD)
Grand Tetons National Park - Teton Range in the background (horst) & Jackson Hole Valley in the foreground (graben).
Grand Tetons National Park - Mt. Moran in the Teton Range in the background (horst) & Jackson Hole Valley in the foreground (graben).
Grand Tetons National Park - Mt. Moran in the Teton Range (horst block).
Grand Tetons National Park - Teton Range in the background (horst) & Jackson Hole Valley in the foreground (graben).
Mt. Moran (above & below) in the Teton Range (horst block). The Teton Range principally consists of Precambrian metamorphic and igneous basement rocks - mostly granites and gneisses. The top of Mt. Moran has a little bit of Cambrian-aged Flathead Sandstone. The erosion surface separating it from the underlying basement rocks is a significant unconformity - a nonconformity (sedimentary rocks unconformably overlying igneous or metamorphic rocks). This is the same surface seen in Grand Canyon, capping the Precambrian basement rocks at the top of the Inner Gorge. This is the “Great Unconformity”.
The dark-colored, subvertical stripe near the top of Mt. Moran is an igneous dike, a planar igneous intrusion that cuts across country rock. It is composed of mafic rocks having crystal sizes between those seen in basalt and gabbro and is called diabase.
