Page:Walcott A Geologists Paradise.djvu/2



The study of the arched block of strata 16,000 feet or more in thickness from which the picturesque  impressive mountains and canyons have been carved has resulted in the discovery that the   in which the great Bow Valley is excavated form a part of the North American continental beds that were deposited in great fresh-water lakes before the waters of the ocean swept over the continent and   their task of depositing the 12,000 feet or more in thickness of rocks of Cambrian age that now contain the remains of the marine life of that period.

As the study of the formations developed it was found that in the eastward thrusting of the rocks massive limestones were often crushed  ground   fragments; in other places the thinner beds for 100 feet or more would be folded and crumbled between huge masses of even-bedded limestones that showed no traces of disturbance. In other places a series of beds, 1000 feet or more in thickness, met some obstacle which they could not crush or surmount, and were driven upward at almost right angles, forming series of sharp, ragged ridges. On the east side of the