124 GEOLOGY OF THE DENVElt BASIN. 



shown in the Laramie basal sandstones has disappeared, the western rim is 

 a secondary fold, west of which, between it and the steeply upturned beds 

 of the foothills, lies a wide area of gentle dip, often not over 10° or lf)°. 

 The eastern rim of the syncline is the same throughout. 



The Eggleston syncline. This lies JUSt Cast of tllC 1 hividsoll SVlU'liue, !lt tile 



eastern end of the Lake mesa. It is exposed as a shallow east-north- 

 east to west-southwest trough in the lower Laramie sandstones and coal 

 measures, the width of which is between one-half and three-fourths of a 

 mile, the axial extent probably between 1 and "2 miles. It is doubtful 

 whether the depression of this syncline is sufficient to permit the horizon 

 of workable coal to appear entire along the center of the trough; in any 

 event the economic value of the coal would be slight on account of 

 proximity to the surface and consequent deterioration by weathering. 

 South and east of this syncline, from the presence of upper Laramie in 

 the bluffs south of Coal Creek and in the valley itself, the beds exposed 

 in the front of the hake mesa must rapidly dip to the east and become the 

 western rim of the Coal Creek syncline. 



The coai creek syncline. — This svucliue, which is a general depression embrac- 

 ing several subordinate troughs, occupies the valley of Coal Creek from 

 its confluence with the Boulder to a point a little west of the crossing 

 of the Denver, Marshall and Boulder Railroad, about 3 miles west of 

 Louisville. Its longitudinal axis is a little over 1*2 miles in length, while 

 the width of the trough from rim to rim will average about 3 miles. The 

 syncline occupies the western side of the lower Coal Creek valley and 

 trends diagonally across the upper valley, its axis Ling approximately 

 northeast-southwest. The northwestern rim lies in the eastern bluffs of 

 the Lake mesa, crosses the Davidson, and, after the break in its continuity 

 occasioned by the Sand Gulch fault, is in general coincident with the ridge 

 Ling between Coal Creek and Sand Gulch. For its northern half the 

 eastern or southeastern rim is clearly defined and lies just west of the 

 lower Coal Creek fault; along its southern half it is less pronounced, but 

 is probably to be found in the low mesa between Coal and Lock creeks, 

 where, however, the northwesterly dip of the strata may have become so 

 slight as almost to render the trough open, and directly continuous in 



