As we float through the grand basement of time on the Colorado River in the Grand Canyon, the rock viewing along the river banks had changed to now start showing us some of the oldest history to be found in the canyon. The sandstone Tapeats layer starts to give way to the metamorphic shist layers of vishnu below.

For even more time-test beauty, the black Vishnu Schist displays a thick stripe of pink Zoroaster Granite. Zoroaster granite is classified as a coarse-grained pegmatite comprised of quartz, alkali-feldspar, mica and hornblende. It is formed by partial melting of the lower crust during its deformation over a billion years ago. The Precambrian Vishnu Schist and Zoroaster Granite are considered to be the basement structures or foundation upon which the overlying strata of the Grand Canyon are built.

For a final bit of mystery, this contrast of the Tapeat and Vishnu rock layers is missing about one quarter of the Earth's total geologic history, which should exist between them! Whether it was deposited there and then fully removed through erosion, or never deposited at all, its really hard for geologists to say, Either way, this break in the geologic history of the area spans about 1.5 billion years!