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The floor on which the Algonkian rests is remarkably even, and here again is proved an interval of incalculable length, during which an ancient land mass of Archean rocks was baseleveled before it received the cover of the sediments of the later age.
It spread out over the Algonkian rocks in small sheets or blankets, which here and there are still to be found to-day. Tilting of the Algonkian Strata. Slowly this twelve thousand feet of strata emerged into the sunlight. In the uplifting processes, the surface of the earth, where they were, became tilted, and these strata therefore "dipped" or "tilted" away from the perpendicular.
After this planation was complete, a subsidence occurred; the whole area became the bed of an inland sea, and upon the planed-down granite, the debris that formed the Algonkian strata was washed.
Walcott spent a winter studying the Algonkian strata of that region. To the west is Point Sublime, Powell Plateau, and other scenery of an unusually majestic character. Features of the North Wall. But let us now return to the main north wall before us.
The vast length of Algonkian time is shown by the thickness of its marine deposits and by the cycles of erosion which it includes. OTHER PRE-CAMBRIAN AREAS IN NORTH AMERICA. Pre-Cambrian rocks are exposed in various parts of the continent, usually by the erosion of mountain ranges in which their strata were infolded. Large areas occur in the maritime provinces of Canada.
The upper walls were similar in tint to those in Marble Canyon, but here at the river was a new formation; the algonkian, composed of thousands of brilliantly coloured bands of rock, standing at an angle the one irregularity to the uniform layers of rock a remnant of thousands of feet of rock which once covered this region, then was planed away before the other deposits were placed.
By and by Vishnu Temple, the grandest of the rocky structures, comes into sight, and a little further on one can see, at the base of Vishnu, and above the granite, the red tilted strata of the Algonkian. The descent into Hance Canyon reveals a fine view of Ayer Peak, and as we look down we can see the peculiar shattering of the Tonto sandstones that Thomas Moran named the Temple of Set.
Thus the Algonkian contains the remains of only the humblest forms of the invertebrates. In the Cambrian, Ordovician, and Silurian the invertebrates were represented in all their subkingdoms by a varied fauna. In the Devonian, fishes the lowest of the vertebrates became abundant. Amphibians made their entry on the stage in the Carboniferous, and reptiles came to rule the world in the Mesozoic.
A short run was made after this work was completed. The camp we were just leaving was about three miles above Kanab Canyon. The granite was behind us, disappearing with a steep descent much as it had emerged at the Hance Trail. There was also a small deposit of algonkian. This too had been passed, and we were back in the limestone and sandstone walls similar to the lower end of Marble Canyon.
The granite was broken down at this point, and another small deposit of algonkian was found here. There were intrusions, faults, and displacements both in these formations and in the layers above.
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