100 JOSEPH P. ID DINGS 



Slough Creek. It is exposed for a short distance only, being" 

 covered at both ends by volcanic rocks. A still smaller one was 

 observed six miles farther north. These indicate the presence 

 of fractures parallel to the profounder faults. 



North of the body of crystalline schists a northwest fault 

 exists in the valley of the East Boulder River ; another is situated 

 south of Livingston Peak ; and two smaller faults occur between 

 this mountain and Livingston. Two more are located just west 

 of the Yellowstone River in this vicinity ; and there is a short 

 one northwest of Mount Ellis, in the central western margin of 

 the quadrangle. 



The presence of major fractures in a northwest-southeast 

 direction being clearly established, the occurrence of parallel 

 fractures of minor importance is rendered highly probable, some 

 in fact, having been observed in the field. 



Corresponding to these northwest-southeast fractures are the 

 channels of many of the tributaries of Slough Creek, Buffalo Creek, 

 and Hell Roaring Creek ; the minor branches and the main chan- 

 nels of many of the streams flowing into the Yellowstone, as far 

 as Livingston, notably those in the Gallatin Range. The most 

 remarkable instance, which is a good example of a fault valley, 

 is the valley of East Boulder River. 



Returning to the consideration of the course of the Yellow- 

 stone River, it is seen that upon leaving Yankee Jim Canyon it 

 flows at right angles through a broad valley in a northeasterly 

 direction for forty miles. More strictly, the first twenty miles 

 are about N. 30° E., the next sixteen miles being more northerly. 

 From the mouth of Shields River beyond Livingston the course 

 is south of east, nearly at right angles to its course at Livings- 

 ton. This is followed by a right-angled bend at McAdows 

 Canyon, after which the course is northeast to the edge of the 

 quadrangle. 



The broad valley of the Yellowstone between Yankee Jim 

 Canyon and the Lower Canyon, which valley continues south- 

 west up Tom Minor Creek, lies in the direction of a scarp fault 

 forming the western flank of the Snowy Mountains. The sum- 

 mits of gneiss and schist at 1 1 ,000 and 1 0,000 feet from Emigrant 



