102 GEOLOGI OF THE DENVER BASIN. 



detected al certain points. A measurement from tliis line to the base of tlie coal 

 seam was made at one place and showed L,700 feel of the upturned edges of Laramie 

 strata. Ii is probable thai we here Lave the very base of the formation. 



The geology of Golden is very complicated, but my observations led me to con- 

 clude thai during the upheaval of the Fronl Range a break tnusl have occurred along 

 a line near the western base of Table Mountain, forming a crevice through which 

 issued the mailer that forms the basaltic cap of these hills. The eastern edge Of 3 

 broad strip of laud lying to the west of this break dropped down until the entire strip 

 of land assumed a vertical position or was tilled somewhat beyond the perpendicular. 

 This brought the Laramie <>u the east side of the Cretaceous, with its upper strata at 

 the extreme eastern, while the coal seam at its base occupied the extreme western 

 Side of I he displaced rock. The decree of inversion varies slight ly at different points 

 and may have been much greater in some places. This will probably account for the 

 discovery at one time of a certain Cretaceous shell (Mactra) above a vein of coal in a 

 shaft aboul I miles north of Golden, and about winch considerable has been said in 

 discussing the age of the Laramie group. 1 visited the spot, but found the strata so 

 covered by wash that I was unable to determine their nature. 



In the above views there arc four points requiring notice, although 

 one — that regarding a certain Cretaceous shell — is somewhat irrelevant. 

 The lii'st point is the remark as to the couformability of all the strata from 

 the Denver beds to the Montana group. Although no discrepancy in dip 

 or strike is noticed between them in the vicinity of the Table Mountains, a 

 study of the whole region has abundantly proved the existence of several 

 unconformities, by evidences of erosion, by the areal distribution oi the 

 outcrops, and by the character of the component materials of the various 

 formations. The second point is the crevice near the western base of Table 

 Mountain, through which issued the basalt of the region. As a matter of 

 fact, no evidence of such a crevice, nor of the dike which would still 

 remain as its tilling, exists along the well-exposed base oi the hills. 

 Furthermore, the outpouring of the basaltic sheets is entirely accounted 

 lor liv the great Ralston dike and the irregular eruptive body near its 

 southern end, and hence there is no necessity for assuming a further 

 fracturing of the strata to give it a vent at some other point in the field. 

 The third point, the fault, into which 1'rol'essor Ward has developed the 

 break, beyond a doubt coincides iu locality with the greal fold which 

 occurs all along the eastern base of the Colorado Range, by which the 

 beds to the west >d' it are sharply upturned, often to a vertical or reversed 



