coal. 355 



It is possible that instead of ending', as indicated on the map, in the Harper 

 fault, it may continue on its trend across the valley of Coal Creek and 

 enter the Bluffs on the opposite side, at a point a little southeast of that at 

 which the Denver, Marshall and Boulder Railroad crosses the creek, a 

 marked irregularity in position and association of sandstones and shales in 

 this vicinity suggesting this. In either case the strata southeast of the 

 fracture have been raised, and, as the effect of subsequent erosion, the 

 outcrop of the coal horizon has been carried to the cast a considerable 

 distance from the line of fracture. 



From opposite Louisville eastward to the vicinity of Canfield the 

 outcrop of the coal horizon lies either directly along the top of the ridge 

 separating Sand Grulch and Coal Creek or just below the crest, on its 

 western slope. In this distance the coal shows only in tine particles in the 

 soil, or in an occasional drill hole or shaft, hut this, with the exposures of 

 Fox Hills and of the basal sandstones of the Laramie, is sufficient to define 

 the horizon. 



The strike along this portion of the rim is about N. MO E.. the dip 

 from 5° to 15° ESE. 



At the northern end of the ridge and beyond, in the valley of 

 Boulder Creek, the outcrop is carried to the east into the flatter portion 

 of the syncline, and the dip reaches its minimum. The coal horizon now 

 passes beneath the Quaternary deposits in the forks of Boulder and Coal 

 creeks, rounds the point of land between them, and reappears at water 

 level in the latter creek near the railroad station at Erie. From this 

 point northward it gradually rises to the level of the flood plain, and 

 thence enters the bluffs on the east side of the valley about a mile below 

 town. The outcrop then continues northward, rising to the general level 

 of tile prairie, whence it shortly passes into the lower Coal ('reek fault. 

 With this the western rim of the syncline is complete. 



Eastern rim. — The eastern rim of the syncline in the northern half of 

 the field is formed by the upward bend of the strata in the fold just west 

 of the lower Coal Creek fault, in which fold the fault had its origin. The 

 general features of the fold and fault are: The opposition of the Fox Hills 

 and upper Laramie, on the west and east of the fracture, respectively; the 



