182 GEOLOGICAL SURVEY OF THE TERRITORIES. 



f 



The flatness of tlie dip near tlie Butte is probably due to the effect of 

 this fold. 



■4r Southward along the east slope of this fold the valley widens before 

 its contraction at the Lower Muddy Butte. On the w^est, the slopes 

 coming from the anticlinal ridge are less cut up by intersected ravines 

 than at the north, the terraces being more continuous and longer, run- 

 ning from the ridge in long flat slopes, and falling in one or two steeper 

 descents to the river. On the east side of the river the lake-beds have 

 here been more extensively eroded away than at the north, and the 

 sandstones of No. 5, being here quite flat, are exposed with their west- 

 ern edges showing in low escarpments facing the river. Back, (east- 

 w^ard,) they disappear beneath the ridge of the lake-beds which sepa- 

 rate the Muddy from the Troublesome. West of one of these flatly dip- 

 ping tables of No. 5, and about five miles north of the Lower Muddy 

 Butte, and a little south of section 3, some of the Cretaceous beds are ex- 

 posed in the face of the lake-bed covered river-bank, and show a folding 

 of the formation along a north and south line, the dip to the west being 

 450, that to the east at first 20°, flattened to about 10^. The horizon 

 again brought to the surface is probably the No. 3 limestones. Here, 

 then, is another anticlinal fold indicated. It was not directly traced 

 southward, and since the soft beds have been leveled by erosion, and 

 probably almost wholly covered by lake-beds, there are no easily traced 

 surface features to indicate its extent or nature. A few exposures on 

 the east side of the stream, and a little south of this point, would seem 

 to show that the beds on the east side of the fold were swinging some- 

 what eastward, as if to pass to the east of the Lower Butte, but they 

 then become concealed by the ridge of lake-beds. This fold is indicated 

 in section 3. 



A pretty constant outcrop seems to be of a harder horizon of sand- 

 stones in Cretaceous No. 5. These usually outcrop east of the river, 

 and, as indicated on the map, seem to show the effect of these two folds 

 in their line of strikes. At first quite flat, the outcrop in going north 

 gradually steepens, and trends more and more west, till, on a northwest 

 strike, it forms a hog-back ridge nearly 200 feet high, and dipping 40^ 

 northeast. It would seem to be here running around the north end of 

 the eastern fold, but, feeling the influence of the western fold, it turns 

 more northward. Again it runs northwestward, as if tending to mantle 

 around the northern end of the latter fold, but near the Upper Butte it 

 turns northward, probably farther north to swing west again. 



The Lower Muddy Butte is a high knob rising abruptly on its north 

 and west sides to a height of about 1,800 feet above the river. It is of 

 granite, with its base almost wholly surrounded by the low-lying lake- 

 beds, and is probably the northwestward extremity or arm of the gran- 

 ite mass shown to exist along the lower portions of the Grand. 



Westward, but a few miles from the Butte, and across the narrowed 

 valley, may be distinctly seen the limits of the Lower Cretaceous quartz- 

 ites and sandstones, as they lie up against the granite of the Park 

 ridge and dip down eastward toward the Butte. The broad, low valley 

 stretches northward, and occasional outcrops of its Cretaceous rockg 

 may be seen beneath tlje terraced slopes; but in this direction, as said 

 before, all is so leveled and covered with the terraces that the relations 

 of the Cretaceous to the granite of the Butte are not apparent. Whether 

 the former are upturned against the Butte, or whether a fault separates 

 the two, or whether the Butte may not represent an elevation of the 

 granite which existed before the Cretaceous beds were laid down sur- 

 rounding it, is not readily seen. The abruptness of the hill, the apparent 



