134 GEOLOGY OF THE DENVER BASIN. 



from the west around the bluffs of the Davidson mesa. The southern end 

 of the fault is lost in the mesa, but it is probably not far from the north- 

 and-south road that crosses just west of the Davidson property. The 

 northern end has been taken at its intersection with the northern fault, near 

 the railroad, although it is not at all unlikely that one or the other of these 

 fractures may extend a little beyond the point of intersection, especially as 

 both faults were apparently well developed in the immediate vicinity. 

 Indicating- this possibility, the southern fault has on the map been extended 

 to the northeast in a dotted line. 



The northward extent of the northern fault is unknown; it is com- 

 pletely lost in the lowlands of the valley about 2 miles north of the 

 fortieth parallel. 



Both of the Davidson faults are of the reverse type; the downthrow 

 is east and the stratigraphic displacement about 200 feet, though toward 

 the southern end, near the Davidson coal held, it may reach 300 feet. The 

 opposing strata are a horizon of the Fox Hills, about 60 feet below its 

 summit, on the west of both fractures; on the east, along the north fault, 

 the upper portion of the sandstone lb along the south, this sandstone 

 with the overlying coal measures. In the immediate vicinitv of the frac- 

 ture the strata on both sides are locally somewhat disturbed: on the east, 

 the Laramie bend down toward the fault; on the west, the Fox Hills like- 

 wise bend downward toward the fault, and also show a number of minor 

 flexures, diagonal to the trend of the fault, notably along the northern 

 break between the railroad and a mile north. 



The Sand Gulch and Harper faults. Of tllCSC till" Salld Grlllchfault is tllC UOrtll- 



ernmost and closely follows the topographic depression of this name for 

 its entire length. At the head of the gulch it intersects the Harper fault, 

 which follows the southeastern base of the Davidson mesa, above the town 

 of Louisville. It is quite possible that these constitute a single, curved 

 fault, but this can not be determined. 



The Sand Gulch fault belongs to the N. 30° E. series of fractures. 

 Within Kin or 200 feet of it the strata on both sides are considerably 

 crumpled, but beyond their dip is apparently away from the fault, front 

 a gentle angle up to 20°. The evidence of the fault is the superficial 



