BROWN'S PARK ASPEN MOUNTAIN DISTRICT. 209 



its different portions. Prior to this downthrow there was a great elevated 

 valley drained into the Green River. When the downthrow commenced it 

 is probable that the Brown's Park beds were not yet deposited, but after it 

 had continued for some time the region was so depressed that the waters of 

 the stream were ponded and a lake formed. In this lake, then, the Brown's 

 Park beds were accumulated. 



We know that the Brown's Park beds were involved in a part at least 

 of this downthrow, and hence were deposited before the downthrow was 

 accomplished, because the beds themselves were involved in the displace- 

 ment; they are severed by faults and bent by fractures where they are seen 

 to overlap or extend beyond the area of downthrow. 



Hence it is seen that Brown's Park is not a valley of displacement 

 o'r of subsidence, but was originally formed as a valley of degradation an 

 elevated valley in a mountain region. It subsided or fell down as a part of 

 a greater block. But the whole of it did not thus subside, for the Dry Mount- 

 ain's stand across the site of this ancient depression. 



ASPEN MOUNTAIN DISTRICT. 



In this district we have a great upheaval with its axis in a north and 

 south -direction, at right angles to the Uinta upheaval. On either side of 

 the upheaval there are zones of maximum flexure. 



The beds brought to view in the degradation of this upheaval are all 

 the Cretaceous formations above the Henry's Fork Group and all the Cenozoic 

 groups below the Brown's Park; hence the inception of this upheaval dates 

 from some epoch in Post-Bridger time. The whole of the uplift is not within 

 the area embraced in the map. The section, together with the geological 

 map, presents all the important characteristics of this uplift, but there are 

 some minor features of interest. In the northwest, northeast, and southeast 

 angles or corners of the uplift there are many minor faults normal to the 

 strike of the beds. Quien Hornet Mountain stands on the southwest corner. 

 No faults have been discovered here. 



There is. a gentle synclinal between the end of the Aspen Mountain 

 uplift and the side of the Uinta uplift. At the south end of the uplift the 



axis passes through the eastern end of Aspen Mountain. Farther north- 

 14 P o 



