More than 700 million years elapsed between intrusion of the black dikes
and deposition of the first Paleozic sedimentary rocks—a longer period
of time than has elapsed since the beginning of the Paleozic Era. During
this enormous interval the Precambrian rocks were uplifted, exposed to
erosion, and gradually worn to a nearly featureless plain, perhaps
somewhat resembling the vast flat areas in which similar Precambrian
rocks are now exposed in central and eastern Canada. At the close of
Precambrian time, about 600 million years ago, the plain slowly
floundered and the site of the future Teton Range disappeared beneath
shallow seas that were to wash across it intermittently for the next 500
million years. It is to the sediments deposited in these seas that we
turn to read the next chapter in the geologic story of the Teton Range.
[Illustration: Figure 30. _A glance at the yardstick. The geologic
time scale shows positions of principal events recorded in the
Precambrian rocks of the Tetons._]