PEALE.J DESCRIPTIVE GEOLOGY — BANNACK RANGE. 571 



ceous scliist. I tliiuk there is uo doubt that the beds are identicaL 

 The dip of the beds in the section just given is approximately east, at 

 an angle of 55°. The strike therefore must be about north and south. 

 This probably curves a little to the eastTv^ard toward the south, as we 

 find near the divide to Malade Yalley an anticlinal axis which is in all 

 probability the same noted in the canon of the Portneuf. The axis of 

 ' the range, therefore, lies to the Avest of the station, and the beds must 

 sink as we go south, for the southern part of the range is made up of 

 the limestones that lie above these quartzites. Station 78, just south 

 of 77, is on the micaceous slates that lie beloAv the quartzites and chlo- 

 ritic slates. It is a couple of hundred feet higher than Station 77. 

 South of Station 78 a long ridge connects the northern portion of the 

 range with the southern, on which Station 135 was located. 



Station 135 is on limestones that are probably Silurian. Toward the 

 base quartzites outcrop, probably the top of the Cambrian. The dip on 

 the station is about west. On the slopes leading to the station there 

 appears to be some curving in the strike, so as to make the dip more to 

 the southward or soiithwest. On the east side of the Malade Divide 

 the dip appears to be from ]^orth 17° East to S"orth 27° East. 



Between the two points, therefore, there must be an anticlinal axis which,. 

 I think, is the same as that of the northern part of the Bannack Range. 

 The lowest outcrop noted on the east is a white quartzite, above which are 

 irregular-structured limestones. They soon disappear as we get down 

 into Marsh Creek Yalley. Bradlej?- considered these limestones as be- 

 longing to the Quebec Groui^.* I found no fossils in the beds, but they 

 are probably the same as the limestones outcropping south in Malade 

 Valley, bacJi of Malade City. The mountain mass Avest and south of 

 Station 135 may be partlj^ Carboniferous — the continuation of the Car- 

 boniferous south of Samaria, yet to be described however. The western 

 side of the range and the A^alley beyond were not examined, and this 

 ojiinion is, therefore, merely conjecture. 



Xorth of the Portneuf Canon the prolongation of the Bannack Eauge 

 is a ridge forming the western portion of the hills west of Mount Put- 

 nam. On these hills the outcrops are obscure; on Station 80 a gray 

 quartzite shows which is the continuation of one of the quartzites farther 

 south. The dip could not be determined. North of the station the Cam- 

 brian beds seem to disappear beneath Tertiary (Pliocene) deposits, which 

 form the hills south of Eoss's Fork of Snake Eiver. They, however, 

 form cappings, for at several i)laces outcrops of limestone were seen 

 protruding above the light, white, and reddish Tertiary beds. 



On Station 81, eight or nine miles north of Station 80, basalt is found 

 on the summit of the hills bordering the valley of Eoss's Fork and that 

 of Snake Eiver. This basalt dips at quite an angle toward the valley, 

 and on some of the hills appears to be horizontal. The Tertiaries also 

 show dips toward the valley of Snake Eiver. South of Station 81 a hill 

 shows outcrops of blue limestone, probably Silurian, with a northern 

 dip. All about the hill Tertiary limestones and sandstones outcrop, con- 

 cealing the older beds. The basalt appears much older than the basalt 

 of Marsh Creek, and its position on the Tertiary (Pliocene?) proves it 

 older. It was probably uplifted with the underlying beds, which places 

 its age as subsequent or just at the close of the Pliocene. The source of 

 this basalt is probably some point in the Snake Eiver plain. Basalt is also 

 found in the valley of the Portneuf, extending up the valley from the Snake 

 Eiver Valley. This basalt of Station 81 is older. In the former, Professor 



* Report U. S. Geol. Survey, 1872, 1873, p. 203. 



