352 GEOLOGY OF THE DENVER BASIN. 



The mines of the district are the Dunn and several unimportant and 

 abandoned openings on the Davidson property. The Dunn, which affords 

 the above section, is worked only periodically, to supply local demand. 



IRE EOGLBSTON SYNCLINE. 



This separates the southern ends of the two great synclines of this 

 portion of the Denver Basin, the Davidson and Coal Creek. It is of 

 limited area and lies almost wholly north of Coal Creek, in the southern 

 and eastern portion of the Lake mesa. It is separated from the Davidson 

 syncline by the anticline which crosses this mesa just east of the Lake 

 basin, but is apparently united with the Coal Creek syncline by an open 

 southern end. Its northern end is very shallow, the trough gradually 

 deepening southward. The trend of the syncline is northeast to southwest. 

 Tlie northern end shows in a slight depression in the basal sandstones of the 

 Laramie in the ditch at the eastern end of the Lake mesa. In this portion 

 of the trough the coal measures barely escaped complete erosion in the 

 wearing down of the region before the deposition of the Quaternary cap. 



The outcrop of the coal horizon beneath the Quaternary probably 

 joins that of the Davidson syncline, opposite to and near the southeast 

 corner of the Lake basin; from here it passes eastward, then southward, 

 and, after a somewhat tortuous trend, appears in the bluffs of Co;d ('nek 

 near Sweeney's ranch, where the measures strike N. 30° E. and dip 15° to 

 the northwest, forming here the eastern side of the syncline. 



The coal horizon, exposed at Sweeney's, crosses Coal Creek half way 

 between this and the Eggleston ranch to the west, where openings have 

 been made in a low bluff bordering the bottom on the south side of the 

 stream. The coal, according to report, for it could not be seen, here dips 

 to the west, but it shortly takes on a southern dip, changing to southeast, 

 and passes beneath the high mesas south of the creek. The center of the 

 Kggleston svncline in the Lake mesa is occupied by the upper Laramie 

 shahs, hut owing to the comparatively shallow depth of the trough only 

 the lower beds of the series at present exist — in all, perhaps, 200 feet. 



The thickness of the coal at the two openings in the Eggleston 

 syncline is reported to lie from 2 to 3 feet. But little has ever been mined, 

 and this only for trial by farmers. 



