Lower Yoho Valley the limestones of Mount Ogden are lying nearly level, but on the eastern slope above Sherbrooke Lake Canyon the same beds are turned down at right angles and disappear beneath the canyon bottom. Everywhere the keen eye of the geologist will find evidence of mountain-building on a grand scale.
The panoramic photograph, taken by the author from Burgess Pass, 3,000 feet above Field, and published as a Supplement to this number of the National Geographic Magazine, shows at a glance over 9,000 feet in thickness of bedded rocks, 6,000 feet of it in an almost sheer cliff in the mass of Mount Stephen. Many thousand feet more may be seen to the westward in Mount Denis and in Mount Vaux. From Mount Stephen the eye follows to the left across the great canyon of the Kicking Horse River to the summit of Mount Field, two miles away, where the same limestone and shale beds carrying the same fossils indicate that thousands of feet in thickness and many millions cubic yards of hard rock have been removed by erosion from between the two mountains, Stephen and Field. From Mount Field a gentle slope carries the same beds northward through Mount Wapta, where they undulate across the President Range and plunge to the westward beneath the corrugated and more readily broken Ordovician rocks of the Van Horne Range.
EARLY MARINE LIFE
All of the Cambrian rocks were deposited in waters teeming with marine invertebrate life. As far as now known, this was before the day of fish or of any other vertebrate animal; land plants and even marine vegetable life were almost unrepresented. Other animals of the sea, however, existed in great profusion, and here and there conditions were so favorable for their burial in the mud and sand of the Cambrian sea that they were preserved unbroken, and throughout all the processes of rock-making and mountain building they have escaped destruction.
In one of these favorable places the most delicate of organisms, like the jellyfish, have been exquisitely preserved and we have crustaceans of many varieties. Among these many preserve the most delicate branchiæ and appendages, and one can hardly realize that they were buried in the mud 15 to 20 million years ago and have remained undisturbed while several miles of thickness of sediment were deposited over them, changed into rock, elevated into mountain masses, and later eroded into the present mountains and canyons.
We have long considered that the trilobite (page 516) was the most highly developed animal in the Cambrian time, but last summer a crustacean was found by the author in the fossil bed near Mount Wapta that was the king of the animal world in its day (page 517). That it was prepared to assert its right to the control of the Cambrian sea is shown by the claws with which it was armed.
To the geologist interested in the volcanic rocks a great field is waiting in the Selkirks to the west, and for generations to come there will be unsolved problems for the special student in this great region of mountains, glaciers, and rivers.
SUMMARY OF GEOLOGIC FORMATIONS
In the long panoramic view the rocks seen in the distance, forming Mount Balfour, belong to the Sherbrooke formation of the Upper Cambrian, or the most recent rocks of the Cambrian section. Beginning with these and going downward, the following formations are passed through:
UPPER CAMBRIAN
Sherbrooke formation (mainly limestones) |
1,375+ |
Paget formation (limestones and shales) |
360+ |
Bosworth formation (limestone and shale) |
1,855+ |
Total Upper Cambrian |
3,590+ |
