Figure 36. Conglomeratic basal bed of Flathead Sandstone and underlying Precambrian granite gneiss; contact is indicated by a dark horizontal line about 1 foot below hammer. This contact is all that is left to mark a 2-billion year gap in the rock record of earth history. The locality is on the crest of the Teton Range 1 mile northwest of Lake Solitude.
Once again the shoreline crept eastward, the seas cleared, and the Gallatin Limestone was deposited. The Gallatin, like the Death Canyon Limestone Member, was laid down for the most part in quiet, clear water, probably at depths of 100 to 200 feet. However, a few beds of “edgewise” conglomerate indicate the occurrence of sporadic storms. At this time, the sea covered all of Idaho and Montana and most of Wyoming ([fig. 35B]) and extended eastward across the Dakotas to connect with shallow seas that covered the eastern United States. Soon after this maximum stage was reached slow uplift caused the sea to retreat gradually westward. The site of the Teton Range emerged above the waves, where, as far as is now known, it may have been exposed to erosion for nearly 70 million years ([fig. 35C]).
The above historical summary of geologic events in Cambrian time is recorded in the Cambrian formations. This is an example of the reconstructions, based on the sedimentary rock record, that have been made of the Paleozoic systems in this area.
Figure 37. Cambrian fossils in Grand Teton National Park.
A-B. Phosphatic-shelled brachiopods, the oldest fossils found in the park. Actual width of specimens is about ¼ inch.
C-D. Trilobites. Width of C is ¼ inch, D is ½ inch. National Park Service photos by W. E. Dilley and R. A. Mebane.
A.
B.