TEIE REGION ABOUT GOLDEN. 83 



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The aiva affected 1>\- the phenomena now t<> he discussed extends 

 along the base of the foothills of the (John-ado Range west of Denver, from 

 a point about a mile south of Bear Creek northward to Coal ('reek, a 

 distance of 21 miles, with a breadth varying from 2J, to 4 miles, the greater 

 occurring along its northern and southern edges. It involves the hogbacks 

 of the Dakota and the region within to the Archean, and includes the 

 prairies as far to the east as Mount Carbon, the western slopes of Green 

 Mountain, the Table Mountains, and the vicinity of the Ralston dike. 



Topography. — The topography shows a marked variation from that normal 

 for the foothills region in general, and its relations to the geology of the 

 tract as displayed from point to point are so close as to warrant the asser- 

 tion that for every topographical lineament there is to be discovered an 

 equivalent geological incident that has led to its development. For mile 

 after mile along the mountains the normal topographical features may he 

 traced with unswerving regularity, hut within the area to he described 

 they undergo rapid change, and midway the length of the tract, in the 

 vicinity of the town of Golden, they are lost to recognition. For a dis- 

 tance of over a mile north of the town, and an equal distance south of 

 it, the Dakota hogbacks have completely disappeared; the low Niobrara 

 ridges cease to exist at a point about a mile north of Bear Creek, not 

 to appear again until the region of Van Bibber Creek, 10 miles to the 

 north, is reached; the Laramie sandstones with their coal have gradually 

 approached to within 500 feet of the Archean at Clear Creek, the vari- 

 ation in their strike from that of the Triassir and Dakota outcrops below 

 being apparent to the most casual observer; finally, opposite the center 

 of this great topographical gap, appear the two great basalt-capped sedi- 

 mentary masses i '.' North and South Table Mountain, originally continuous 

 but afterwards cut by the waters of Clear Creek, which debouches from 

 the main range midway their length. 



surface delineations. — Keen from any of the more elevated points within 

 this remarkable area, another set of features, second in prominence only 

 to the ones already referred to, at once strike the eve. These are 



