OCR Text |
Show OLASSIFlOATION OF VALLEYS. 161 lesser inclination of the rocks. Second, the texture of the beds-that is, their greater or lesser degree of heterogeneity. The third class of modifying influences is found in the eruptive beds. The last mentioned agencies are not found in the region under imme-diate discussion. · No sharp line of division can be drawn between canons and valleys. For convenience, we designate intervening depressions, caused by erosion, canon valleys, but all these excavated basins, troughs, and channels will be included under the general head of valleys, and the above terms will be used in describing them. I should remark, farther, that species a.re not found in structural geology, if we use that term as it has heretofore been used in the description of organic nature; that is, thet·e are no definite "hard and fast" lines of demarkation between valleys of one class and those of another, and the classification rests solely on typical examples. With these terms before us, let us again describe the valleys of the Uinta Mountains. The canons through which the river passes from Flaming Gorge to Bee Hive Point are anaclinal. Red Canon is obliquely anaclinal; Brown's Park is anticlinal; the Canon of Lodore is cataclinal; Whirlpool Canon above is anaclinal where it runs into a fold, and then obliquely cataclinal in cutting through the other side of the fold. Split lt1ountain Canon is at first anaclinal, then along its central course anticlinal, and at its foot, where it runs out on the opposite side of the fold, is cataclinal; hence it is structurally compound. This is the relation it bears to the minor fold of Split Mountain; but it bears another relation to tho great fold of the Uinta Mountains, and is complex. Hence it is a compound, complex valley. The canons and valleys heading near the summit of the range running with the strike of the rocks into Green River, as above mentioned, aremonoclinal. A good example of this is Summit Valley. Those on tho . north, which head near the summit of the range, and~ running down the flank, tw·n into Green River, are, in their upper courses, cataclinal, and when they turn to follow the strike of the rocks into Green River, are monoclinal. Those 21 COL |