OT.JOHS.] M'COY CEEEK CAEIBOU EEGION. 391 



the section it also possesses much additional interest in the perhaps 

 more or less local stratigraphic derails here displayed and the fauna ob- 

 served in connection with some of the beds. It would appear that the 

 greater portion of the outlying eastern flank, in which a well-defined syn- 

 clinal fold exists, also is occupied by beds of Jurassic age. But in the 

 border of this slope, in the area of the foreland bench, it may be possi- 

 ble the sandstones and arenaceous shales of the Triassic "red-bed" 

 series make their appearance in the regular descending order of their 

 stratigraphic sequence, although their identity is open to question. 



From the summit the topographic and stratigraphic relations of this 

 mountain ridge are well displayed. It is stratigraphically identical with 

 the high dominating ridge west of Station XXVI, and almost due north- 

 west of the present station, the crest of the anticlinal being traced al- 

 most continuously between the two points, though it is broken through 

 by the valley of McCoy Creek in the foreground. To the northeast of 

 this fold in the strata the synclinal depression shown in the foregoing 

 section also has its counterpart in the depression between the dominat- 

 ing ridge and Station XXVI, the beds curving up in a broader, flat- 

 topped arch in the latter station. The sketch introduced in an accom- 

 panying plate will convey a clearer idea of the features here alluded to. 

 The broken and more wooded eastern slopes exhibit less satisfactorily 

 the stratigraphy and structural features, though in the declivities on the 

 lower course of the valley of McCoy Creek the beds show moderate 

 southwesterly inclination which continues to the debouchure. It seems 

 almost certain that these formations in the region on and south of 

 Pyramid Creek, in the vicinity of XXVI, have been bidged up into a 

 broad low dome of very irregular contour, the exact extent of which it 

 is difficult to define. But as no appearance of such a fold exists 

 in the exposure on McCoy Creek, it is probably confined to a belt, the 

 middle of which lies near the debouchure of Pyramid Creek canon, ex- 

 tending north and south from points within or but little extended be- 

 yond the limits of Stations XXV and XXVI. The northeastern border 

 of this uplift, as has already been remarked, includes a narrow zone of 

 greatly disturbed and complicated strata along the border of the moun- 

 tains, which runs out into the Snake Valley before reaching McCoy 

 Creek. This zone may extend north as far as Fall Creek though it is 

 thought more probable that it ceases soon after passing Pyramid Creek, 

 to the north of which the flow of volcanic materials has concealed what 

 the erosion of the valley left untouched. Looking westward, stretches of 

 McCoy Creek may be seen, and in the north side-hills there occurs a 

 fine display of a broad, low, anticlinal fold, flanked at the entrance to the 

 upper basin by an extraordinary uplift and. partial overthrow which will 

 receive fuller notice in the description of the McCoy Creek section. 

 This broad fold is indicated by wide areas of comparatively gentle drain- 

 age slopes in the broad ridge intervening between Station XXVII and 

 Mount Caribou (XXVIII) nine miles to the westward, south of which, 

 owing to the wooded nature of the low mountains in that quarter, nothing 

 was clearly made out in regard to its further extension and character. 

 But in the low southern prolongation of the range, patches of red appear 

 in the steeper slopes, doubtless showing the prevalence in that section 

 of the same series of strata which fills the space between the above- 

 mentioned stations. To the north round into the southeast the great 

 barrier front of the Snake Eiver Bange walls the lower valley of the 

 Snake and Salt Bivers, the southwest slopes supported by short rocky 

 buttresses and scantily wooded. Here and there the view penetrates 

 into the heart of the mountains, where high summits and ridges with 



