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Below this is found the Archaean rock. It is hard for any but the well-trained observer to realize that practically the same conditions that exist on the north wall, exist on the south wall, directly under his feet, except that the Algonkian is absent. The talus shuts off the view, and it seems impossible that there can be such great precipice walls as the opposite mural face reveals.
Planed and smoothed off as they are, the Algonkian and Archaean masses are to be submerged once more in the ever receptive ocean. A period of subsidence occurs, and the whole area is soon hidden under the face of the sea. But, all around these are masses, some day to be mountain peaks, that refuse to sink again into the sea. Then the forces of the air assail them.
THE LAKE SUPERIOR REGION. In eastern Canada an area of pre- Cambrian rocks, Archean and Algonkian, estimated at two million square miles, stretches from the Great Lakes and the St.
In some regions there rests unconformably on the Archean an immense body of stratified rocks, thousands and in places even scores of thousands of feet thick, known as the ALGONKIAN. Great unconformities divide it into well-defined systems, but as only the scantiest traces of fossils appear here and there among its strata, it is as yet impossible to correlate the formations of different regions and to give them names of more than local application.
In most of these mountainous regions the lowest strata are profoundly changed by metamorphism, and they can be assigned to the pre-Cambrian only where they are clearly overlain unconformably by formations proved to be Cambrian by their fossils. In the Belt Mountains of Montana, however, the Cambrian is underlain by Algonkian sediments twelve thousand feet thick, and but little altered.
Where red sandstones have contributed largely to its making, as over the Triassic sandstones of the eastern states and the Algonkian sandstones about Lake Superior, the drift is reddish. When derived in part from coaly shales, as over many outcrops of the Pennsylvanian, it may when moist be almost black.
From this spot a fine view is had of the red-wall limestone below and the Indian Garden; and, far below, at the end of Pipe Creek, the peculiar folding of the Algonkian strata. This folding is also to be seen on the other side of the river in the same rocks. Trees, Flowers and Birds. While descending the first mile of trail, one sees plenty of flowers and shrubs, and many Douglas spruces.
Then, for some reason or other, there was a rest for a while a few hundreds or thousands of years and the masses of sediments became cemented into sandstone and shale, which we call the Cambrian formation, or the Tonto sandstone. This is to be seen resting both upon the Archaean and Algonkian from the porches of El Tovar.
When these rocks were upheaved and subjected to weathering, their iron compounds were decomposed. Their iron was leached out and carried away to be laid in the Algonkian water bodies in beds of iron carbonate and other iron compounds. During the later ages, after the Algonkian strata had been uplifted to form part of the continent, a second concentration has taken place.
As they emerged, weathering and erosion began. It is most probable that this process of degradation began and continued while the topmost strata were at or near sea level, so that it was a simultaneous process with the uplift. Erosion of the Algonkian. How many centuries this weathering and washing away process consumed no one knows.
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