STRUCTURAL DETAILS OF THE CONTACT 145 



stone, 20 feet; coarse dark green (glauconitic) sandstone, 4 feet; coarse 

 gray sandstone, 6 feet; brick-red sandstone, with green (glauconitic) 

 layers, 20 feet ; total, 50 feet. The arkose character so noticeable in some 

 of the sandstones higher up in the sedimentary series of the Manitou 

 embayment, and especially in the Fountain (Carboniferous) beds, is 

 almost entirely wanting in the Cambrian, even where it rests directl}^ on 

 the granite. Although the sandstone is, in the main, rather coarse, it is 

 rarely conglomeratic. On or near the granite it sometimes encloses a few 

 small pebbles, but these are almost invariably vein quartz and well 

 rounded or water-worn. 



The best general views of the contact are obtained by the traveler 

 through Ute pass, between one and three miles above Manitou, on both 

 sides of Fountain creek, as shown rather unsatisfactorily in the two 

 accompanying illustrations (plates 15 and 16). The best view of all is 

 one looking eastward from the Colorado Midland railroad, but not repre- 

 sented by the photographs. It is also well exposed for observation in 

 Williams canyon, as already noted, and in Queens canyon, above Glen 

 Eyrie. In all of these general views the actual exposures of the contact 

 have a good degree of continuity, and the successive exposures are seen 

 to lie almost absolutely in one plane. 



Structural Details of the Contact 



In going up Ute pass by the wagon road we come, in less than a mile 

 from the junction of Ruxton and Fountain creeks, to the point where the 

 contact crosses Fountain creek. On the right is a quarry in the glau- 

 conitic (red and green) upper part of the Cambrian ; and on the left the 

 contact is well exposed in a lateral gulch, shown in plate 15, on the right, 

 opposite the bend in the road, the quarry being on the left just around 

 the bend. Farther up the gulch, near the railroad, which is not shown 

 in the picture, the exposures of the contact are very clear and continuous, 

 the white basal member of the Potsdam resting on a plane smooth sur- 

 face of the granite. A few small and well rounded quartz pebbles are 

 seen in the sandstone along the contact, but no granite pebbles, although 

 5 feet above the contact the sandstone shows an occasional line or trace 

 of granite debris — grains of quartz and red feldspar. North of this gulch 

 and immediately above Fountain creek, as seen in the upper right- 

 hand side of plate 15, the almost plane contact is admirably exposed, 

 and the exposure continues around the end of the hill northward to the 

 south side of the next gulch, where the granite has been worn out along 

 the contact, leaving the gra}^ sandstone projecting, unsupported, 10 to 20 

 feet as a smooth, flat ceiling dipping south 15 to 20 degrees. From this 



