140, GEOLOGY OF ASPEN MINING DISTRICT, COLORADO. 
(Section D), Castle Creek flows, has become broader and is slightly over- 
turned against the fault, while the anticline between Castle and Maroon 
creeks is still present and has become shallower and broader. 
Section F—Just east of the eastern end of Section F granite outcrops, the 
distance between it and the Castle Creek fault being very slight. The 
sedimentary beds on the east of the fault constitute, as in Section E, a 
gentle, westerly dipping monocline. Immediately west of the fault the 
beds have a steep but uniform westerly dip, and lie in their normal succes- 
sion. Owing to the northerly pitch of the fold, there are brought into 
outcrop Weber shales, with the intercalated sheet of porphyry which 
usually lies at this horizon. The Weber formation is overlain by the 
Maroon, which is continuous to the end of the section, with the exception 
of the very top of the mountain between Castle Creek and Maroon Creek, 
where the Triassic probably comes in. The general structure of the fold 
along this plane of section is that of a well-marked but open syncline, in 
the bottom of which Castle Creek lies. The relative structure of the beds 
on the east and on the west side of the fault along these different sections 
‘is obscured in large part by the subsequent local uplifting and faulting 
throughout the southern part of the area immediately east of the Castle 
Creek fault. But on comparing this section (Section F) with Section ©, it 
is seen that on the disappearance of the overturned syncline on the west 
there also disappears the slight open syncline on the east; so that from the 
compressed folding at Red Butte there is a change to a more simple structure. 
Section G—Section G is drawn as nearly as possible parallel with the 
general strike of the beds throughout the district, and reaches from 
the extreme northeastern corner of the district shown on the map to the 
western side of the Castle Creek fault south of Aspen. It shows in its 
central part a nearly horizontal intersection with the different beds, while 
the southernmost part is conspicuous on account of the uplifting and 
faulting. In the northeastern part there is a similar but not so sudden 
uplifting, which is also accompanied by faulting, although to a less degree. 
The relation of the Silver fault to the sedimentary beds, as it varies from 
point to point, is better seen here than in any of the cross sections. In 
the northeastern part of the section it separates the Weber shales from the 
Leadville dolomite, and the distance between the fault and the Parting 
Quartzite is comparatively slight. In the Hunter Park area the fault cuts 
