326 GEOLOGTZ OF THE DENYEK BASIN. 



areas are faulted from one another, and the Canfield and Mitchell areas are 

 separated by the eroded cresl of an anticlinal fold or by a local cross-fault. 

 Faults and folds separate the Davidson from the Louisville and Marshall 

 districts, and Ehe White Rock is severed from the others by erosion and a 



succession of faults. The Scrauton is geologically distinct from all others 



h\ its higher horizon. Structurally the coal areas may be grouped under 

 the Foothill region, the Davidson syncline, the Coal Creek syncline, the 

 area east of the Coal ('reek syncline, the White Rock held, and the 

 Scranton field. 



FOOTHILL AREA. 



1 \ lEXL. 



The foothill area includes the highly inclined strata of coal measures 

 along the base of the Colorado Range, and extends from the Marshall area 

 in the north, with which it is continuous, to the vicinity of Wildcat Mountain 

 in the south, in miles beyond the limit of the basin as mapped. South of 

 this latter point no coal is opened or known to exist in workable thickness 

 until the vicinity of Colorado Springs is reached, a distance of nearly T>!) 



miles; north of the basin openings occur here and there as far as Greeley, 

 50 miles from Denver; in both directions, however, the beds are nearly 



horizontal and belong to the prairie class. East and west the foothill area 



is limited, it' the outcrop alone is considered, by the confines of the 



Laramie — indeed, In- the confines of its basal series of sandstones, coals, 

 and shales, which is alone productive in this portion of the basin. The 

 width of the area is therefore only about 250 feet. The beds doubtless 



extend beneath the prairie upon reaching the flexure in which the measures 

 are involved, but they then lie too deep — at least 1,200 to 1,500 I'eet — for 

 present profitable mining. 



