GEOLOGICAL SUEVEY OF THE TEEEITOEIES. 19 



From Mantua to Wellsville, in Cache Valley, tlie surface of the coun- 

 try on either side -of the road is very rugged. The rocks are mostly 

 limestones. The road runs between two ridges of upheaval, or a mono- 

 cliual valley, with the bluish, cherty, brittle limestone rising up 1,500 to 

 2,000 feet on the west side, inclining a little north of east at a very large 

 angle, while on the east side the hills are more rounded, 800 to 1,000 

 feet above the general level of the country, but dipping in the same di- 

 rection. The range of mountains west of Wellsville must average 1,500 

 feet in height ; down the valley are one or two of the highest peaks — 

 over 2,000 feet — which are covered with snow in midsummer. They are 

 composed almost wholly of limestones and quartzites. To the eastward 

 the ridges reach to an unknown distance, becoming lower and the strata 

 inclining at a smaller angle. Instead of beds of massive limestone, there 

 are alternations of arenaceous clays, limestones, and sandstones, Yielding 

 more readily to atmospheric influences, and in consequence the hills are 

 more rounded and covered with grass or small trees. 1 have estimated 

 the entire thickness of the stratitied rocks in this region at 10,000 feet, 

 and it is with this mass that we have to deal at this time. This esti- 

 mate does not include the Tertiary beds, either modern or ancient, which 

 are nearly always present in some form. 



Cache Valley opens into Salt Lake Valley by way of Bear Eiver 

 Bay, and one cannot doubt that the lake itself formerly extended 

 all over Cache Valley. The modern Tertiary or Pliocene deposits 

 which cover the valley jut uj) against the mountains on all sides, 

 with the terraces which are distinct, although not so strongly 

 marked as in Salt Lake Valley. Most of the building rocks at 

 Wellsville are the soft sandstones of the modern deposits, which 

 I have, in a former report, called the Salt Lake group. Compact, rusty 

 brown quartzites enter into the walls of the houses to considerable ex- 

 tent; but for sills, corners, chimney- tops, and other ornamental j)urposes, 

 the whitish-gray and gray-brown sandstones are used, from the fact that 

 they are very durable, and can be wrought into any desirable shape. 

 These calcareous sandstones are horizontal, and underlie the plateaus or 

 terraces in the valley. The quarry near Wellsville is not profitable, as 

 the principal layer of rock is not more than 12 or 14 inches in thickness, 

 and several feet of superficial gravel and marl have to be removed before 

 the sandstone can be obtained. Near Mendon the sandstone is much 

 more compact, and occurs in several layers. It is quite white, and forms 

 very beautiful walls. It varies much in texture, some of it very porous, 

 but it is, for the most part, close-grained enough for durability. It is in 

 some instances a perfect Oolite. At Logan the principal co-operative 

 store, a large two-story building, is constructed of a rock from this group, 

 which is made up of an aggregate of fresh- water and land shells of the 

 genera Limnea, Physa, Vivipara, Helix ^ &c., apparently identical with 

 recent species. I was informed that this rock comes from the foot-hills 

 of the mountains just west of Mendon. It is the upper layer, ^nd is a 

 light-brown calcareous sandstone. The shells are nearly all casts, the 

 rock being soporous in texture that the calcareous shell is in most cases 

 dissolved out. The ridge of elevation, or range of mountains, as it might 

 more properly be called, which forms the eastern wall of Cache Valley, 

 breaks off suddenly near Mendon, and from thence northward it ai3pears 

 in detached portions and of far less magnitude. But the range or ridge 

 which walls in the east side is lofty and continuous. To gain some 

 knowledge of its structure, I ascended Logan Canon about four miles in 

 a straight line above its mouth. The caiion seems to be due partly to 

 a fissure in the Carboniferous limestones and the erosion of the little 



