20 GEOLOGICAL SUP.VEY OF THE TEERITORIES. 



stream that passes througli it. The strata appear to incline each way 

 from the gorge as a sort of axis. There is considerable irregularity in the 

 height of the hills on either side of the canon, but they vary from 800 

 to 2,000 feet. Some of the highest points have banks of snow all the 

 year. The inclination of the strata of limestone varies from 8° to 20°. 

 The greatest dip is at the entrance of the gorge, and as we ascend, it 

 diminishes until it is uniformly about 6° to 10°. One group of strata near 

 the entrance of the canon is 35°. Sonie fragments seem to have broken 

 off of the main ridges, and appear to incline west toward the valley, giv- 

 ing to the section the appearance of an anticlinal. This caBion forms an 

 extremely interesting cross-section of the Carboniferous limestones, and 

 reveals their massiveness and enormous thickness. They cannot be 

 less than 5,000 feet in thickness. The rock is quite hard, brittle, of a 

 bluish-gray color, and in some layers full of seams and cavities of cal- 

 cite. A fine stream, about thirty yards wide and an average of 2 or 3 

 feet in depth, rushes foaming down over the immense masses of rock 

 which have fallen from the mountain-sides into its channel. The local 

 drift is here a conspicuous feature also. It is composed of rounded 

 bowlders, with clays and marls reaching a thickness of 100 to 150 feet 

 in regular and horizontal strata, attached to the sides of the gorge, and 

 showing that, however turbulent the waters, the materials were depos- 

 ited in a lake. At the entrance of the caiion are some remarkable ter- 

 races, composed of sands, clays, marls, and rounded bowlders. The high 

 limestone ridges which bound Cache Valley on the east extend far south 

 of Logan, and immediately at the base are a number of prosperous Mor- 

 mon towns, as Hiram, Paradise, and others. The trend is somev;hat 

 to the east of south, and is composed almost entirely of limestones of 

 Carboniferous age. North of Logan to Smith field, a distance of about 

 ten miles, the quartzites, with variegated sandstones and clays, appear 

 beneath the limestones. Owing to the change in the character of the 

 rocky strata, the symmetry of the range is lost to some extent. The 

 ranges of hills, or of mountains, as they might be called, which bound 

 the west side of Cache Valley, seem to be composed of the same kind of 

 rocks, limestones, and quartzites, for the most part, with i^artings 

 of clay at times. This range separates the two valleys — Malade Valley 

 from Cache Valley. I was not able to make a minute examination of 

 the whole country, including Promontory Mountain, extending far 

 northward, which is occupied by quartzites and limestones which are, 

 probably, mostly of Carboniferous age. From Corinne to Monument 

 Point, along the Central Pacific Eailroad, none but dark, slate-colored 

 limestones can be seen. It would appear, therefore, that a large por- 

 tion of Utah is made up of these nearly i)arallel ranges of mountains, 

 trending nearly north and south, with intervening valleys of greater or 

 less width, which, after their elevation, formed shore-lines for detached 

 lakes or bays. So far as the evidence goes, it would appear that the 

 last lake period of this portion of the West commenced in the Pliocene 

 epoch and continued on up to the present time ; that the waters once 

 filled all these valleys, so that they rested high upon the sides of the 

 mountains, depositing the sediments of the Salt Lake group, gradually 

 passing into the Post- Pliocene deposits which verge upon our present 

 period. It is quite possible that there have been oscillations of level in 

 these modern lake- waters ; but so far as the proofs go, this great inland 

 lake may have continued quite uniform until the Terrace epoch, and 

 that then the waters gradually receded to their present i^osition. If 

 these statements are true, and I believe they are, this country is in- 

 vested with a charming interest to the geologist. 



