coal. 353 



THE COAL CREEB SYNCLINE. 



This syncline, which is a general depression embracing several subor- 

 dinate troughs, occupies the valley of Coal ('reck from a point a little west 

 of the crossing of the Denver, Marshall and Boulder Railroad, several miles 

 west of Louisville, to its confluence with the Boulder, a short distance 

 below the town of Erie. The length of its longitudinal axis is rims a little 

 over 12 miles, while the width <>f the trough from rim to rim will average 

 about ."> miles. The syncline occupies the western side of the lower Coal 

 ('reek Valley, ami Trends diagonally across the upper valley, its axis lying 

 a little nearer the north than the course of this portion of the creek. 



STRUI n Rl 



Western rim. Tile Western Hill of tile ('o;ll ('l'eek SVllclilie lies ill tile 



bluffs on the southeastern side of the hake and Davidson mesas and in 

 the western slopes of the long ridge extending from the latter northeasterly 

 to the vicinity of Erie ami Canfield. In the continuity of this rim there 

 is hut one important break, that near the eastern end of the Davidson mesa, 

 attributable to the Sand Grulch and Harper faults. The general position of 

 this rim is clearly defined. 



Rising from beneath the prairie to the south of upper Coal ('reek, it 

 first becomes distinctly recognizable to the north of the stream in the basal 

 sandstones and coal measures of the lower Laramie, which occupy the 

 bluffs at the eastern end of the Lake mesa. The position of the strata 

 along here is locally somewhat undulating, as they lie in the very crown 

 of the anticline separating the Eggleston and Coal Creek synclines They 

 quickly assume a southeasterly dip of 10 c to 15°, however, passing beneath 

 the Quaternary wash of the valley. A short distance from the base of 

 the bluffs the upper Laramie intervenes between coal measures ami 

 Quaternary, attaining a depth of 100 to 150 feet in portions of the 

 bottom. Whether workable coal exists for an] considerable distance along 



this portion of the rim has not 1 n determined. A bed from 2 to 3 led 



thick is exposed opposite the Sweeney and Eggleston ranches, but its extent 

 is not established. 



In the southern face of the Davidson mesa, a half mile west of the 



MON XX VII 23 



