604 REPORT UNITED STATES GEOLOGICAL SURVEY. 



The terraces are well marked on the north side of the river, as shown 

 in the accompanying diagram. At several places soft marly sandstones 

 outcrop beneath the terraces, especially in the lower ones, with a dip. 

 At the edge of Logan Canon, and extending some distance above its 

 month, are deposits consisting of gravels, sands, marls, and conglom- 

 erate, from 100 to 150 feet in thickness. They are horizontally stratilicd, 

 showing that the lake extended somewhat into the canon at one period 

 subsequent to its erosion, and these beds represent the material brought 

 down by the rapdily flowing stream, which then as now occupied the 

 canon. 



Station 122 was located a few miles northeast of Sinithfield, on a 

 butte that stands out a mile or two from the mountains. The rock on 

 the summit is limestone. Surrounding the butte is a limestone con- 

 glomerate. This butte, therefore, was probably an island near the shore 

 of the lake, whether Pliocene or Post-Pliocene I could not determine, 

 but probably the former, as heavy beds of similar conglomerate were 

 seen farther north which appeared to be of that age. Six or seven miles 

 farther north a similar butte appears, which was not visited. The latter 

 has an elevation of 5,400 feet and the former 5,638 feet. Franklin Butte 

 is much lower and is about four miles west of the edge of the mount- 

 ains. Its elevation is 5,324.* It must, therefore, have been an island at 

 lower levels of the lake. It is composed of limestones, probably Silu- 

 rian in age, although no fossils were seen. On the summit fragments 

 of white limestone were seen resembling the Pliocene limestones, and 

 exactly like the fragments seen at Station 131. If these are Pliocene, as 

 I believe, it may indicate a period of erosion following the uplift at the 

 end of the Tertiary time, and before the Quaternary lake filled the 

 basin of the valley. There are two well-marked terrace leyels on the 

 side of the butte and several minor ones that are not well defined. In 

 the bank of Cub Biver, at Franklin, gravels and loosely aggregated 

 sands show and are horizontal. In the accompanying diagram the pro- 

 file from the butte to the river is shown with the elevations. The upper 

 terrace level is 122 feet below the top, and the lower 437 feet. The sands 

 on the banks of the river are the same as those shown on Bear Biver. 

 East and northeast of the butte are a mass of rounded hills rising 1,400 

 to 1,500 feet above the valley. These do not show many outcrops, but 

 the few seen were of sandstones and conglomerates. I have considered 

 them as belonging to the Pliocene, although it is possible that the con- 

 glomerates may be more modern. It is exceedingly difficult to separate 

 the formations with the limited data at hand. The terraces that are 

 marked on the sides of Franklin Butte are outlined on these hills. 



West of the middle caiion of Bear Eiver these beds, or perhaps lower 

 ones, show, resting on limestones, which appear to have been elevated 

 with them. The outcrops are obscure. The terraces here are compara- 

 tively well marked. 



At the point where the Utah Northern Bailroad crosses Bear Biver, 

 the more modern deposits are well shown, consisting of yellow and red- 

 dish sands, clays, and marls. There is an exposure of about 300 feet. 



Beturning to the south line of our district, and crossing to the west 

 side of the valley, we find the Pliocene beds outcropping again in the 

 foot-hills. At Mendon, a short distance below our line, the sandstones 

 in some of the layers are made up of an aggregation of shells of the fol- 

 lowing genera, IAmnwa, Physa, Vivipara, and Helix. At one of our camps 

 on the Bear, just before it passes into the Gates, there were outcrops 



* By angles of elevation and depression. 



