168 GEOLOGICAL SURVEY OF THE TERRITOEIES. 



in the sandstones which are undoubtedly the equivalents of the beds that 

 bear similar fossils and lie below the breccia east of the u^Dper gate-way^ 

 and near the junction of the Grand and Frazier. It is Cretaceous No. 5. 

 This ridge extends a mile or more from the river, gradually flattening and 

 bending westward. Following down the stream, nothing but river allu- 

 vium is found for nearly a mile, when, along its southern bank beneath the 

 alluvium, there are exposed some 800 feet of black clay, shales, and slates, 

 at first dipping up-stream only 20°, but increasing to 40° farther down. 

 After passing these slates the river breaks through another ridge, but 

 this time of the quartzite and siliceous conglomerates rising out from be- 

 neath the shales, and, like them, dipping 30° up-stream. Behind the first 

 ridge some small longitudinal valleys, with minor ridges of quartzite and 

 siliceous conglomerates with dip lessening to 20° occur, while from 600 to 

 700 feet below, where the quartzite hog-back is first met, the river passes 

 into a caGon cut in a smooth-topped mass of reddish granitic gneiss, thus 

 giving an actual thickness for the quartzite series of about 360 feet. 

 These beds are the Cretaceous No. 1, the shales above being. No. 2, while 

 directly on the line between the two issue the well-known Hot Sulphur 

 Springs of the Middle Park. 



From the granite, ui3on the eastern edge of the map, to the granite 

 below the Hot Springs upon the western edge, the line of the Grand 

 Eiver'passes, therefore, directly across, at least so far as the granites, 

 the Cretaceous, and the volcanic breccia bed are concerned, a synclinal 

 fold, the eastern side of which has some minor flexures, (see section.) 

 Not so the lignitic beds, however. Immediately above the Hot Springs, 

 Mount Bross rises abruptly for over 1,500 feet. It is composed through- 

 out of the characteristic lignitic beds, mainly coarse grits and sand- 

 stones, yellow, gray, and white, with laminated arenaceous shales, 

 which contain many fossil leaves, barely, if any, disturbed from a hori- 

 zontal position. Though direct contact between these and the Creta- 

 ceous in the river at their base was not observed, the position of the 

 mountain is such that its beds must rest unconformably upon the up- 

 turned and eroded edges of the Cretaceous sandstones and shales below. 

 As may be seen in the section, the tops of the great terraces above the 

 lower gate-way of the Grand sweep in long slopes up to White Face 

 Mountain, which is also composed of the lignitic beds, slightly inclined 

 and capped with recent basaltic lavas, which will be spoken of later. 

 The southern face of the mountain is steep, and beneath it the north- 

 west extremity of the breccia ridge disappears. Around the latter 

 appear to sweep the lignitic beds, and to connect directly by a high 

 ridge the west spur of White Face with Mount Bross, throughout which 

 ridge the lignitic strata appear nearly, if not quite, horizontal. The 

 ■western end of the hog-back like ridge of No. 5 sandstone, about a mile 

 above the Hot Springs, likewise seems to disappear beneath the eastern 

 side of Mount Bross, apparently surrounded by its horizontal beds, as 

 is the end of the breccia ridge by the similar beds of the White Face 

 mass. Mount Bross itself shows an indistinct terrace form, though not 

 well pronounced, and its lower terraces in the west run out and appear 

 to quite cover the quartzites of No. 1, if not to reach to and rest directly 

 upon the granites beyond. 



These facts clearly show that here was a loc^l folding of the rocks 

 which occurred hefore the lignitic formation commenced to be laid down, 

 and probably close upon the completion of the deposit of the friable and 

 concretionary sandstones which have been designated as No. 5. Closely 

 connected with this folding, and probably an effect of the same cause,, 

 was the eruption of the material which forms the breccia-bed. 



