126 GEOLOGY OF LI 1 1 : DENVER BASIN. 



northern edge of the upper valley «>t' Coal Creek, where for a considerable 

 distance it is sharply defined by the Harper fault; north of Louisville it is 

 formed of the southeasterly dipping beds that occupy the crest of the ridge 

 between Coal Creek and Sand Gulch; farther oast it becomes continuous 

 with the rim of the Km- syncline. 



The southeastern rim is but indefinitely located along the upper portion 

 of Coal Creek; it probably lies in the bluffs and highlands south of the 

 valley, where, moreover, it has apparently been considerably depressed- 

 Opposite Louisville the trough is defined by the Louisville fault and by the 

 steeply dipping strata involved in a told which lies immediately northwest 

 of this. Upon the disappearance of the Louisville fault to the north o( 

 Coal Crook the syncline probably passes into those of the Lafayette and 

 Mitchell distrii - 



The depth at which the base ot the Laramie is encountered in the 

 trough of the Louisville syncline varies, but in the vicinity ot the town is 

 about 250 foot; it is doubtful if it any whoro exceeds 300 foot. 



The configuration ot the Lafayette trough is loss known than that of 

 any of the subdivisions of the Coal Crook syncline. This is particularly 

 the oaso with the oast side, where, from lack ot exposures, the position 

 of the rim and the inclination of the strata can only bo conjectured from 

 conditi 3 I beyond the immediate basin. It is believed that the 



D rim. after a mile or two south of the confluence ot foal and Rock 

 creeks, - - lerably depressed, and that but a slig-ht rise separates the 

 structurally from the general country beyond. On the northwest 

 the basin is delimited by the Louisville fault, excepting, perhaps, near its 

 northern end. where, the fault having disappeared, the strata become 

 continuous with those oi the Louisville depression, passing with them to 

 the western rim ot the general syncline. To the south the rim ot' the 

 Lafayette basin is that ot the general Coal Creek syncline, while to the 

 north the trough may be directly continuous with the Mitchell subdivision. 

 The base of the Laramie in the axis of the Lafayette trough lies approxi- 

 mately between oOO and 350 feet beneath the level ot Coal Creek. 



Idie Mitchell trough coincides in width with the general Coal "Creek 

 syncline. It is probably continuous to the southwest witli the Lafayette 



