162 GEOLOGY OF ASPEN MINING DISTRICT, COLORADO. 
This has a slight downthrow on the north side. It is probably only a local 
cross fault, running diagonally between north-south faults of the Ontario 
or Tourtelotte Park system and the Silver fault. The main systems of 
faults are shown on this map as on the larger one. West of the Silver 
fault there come in the Schiller and the Sarah Jane, and farther west is 
shown a portion of the Saddle Rock, where it flattens and locally advances 
in outcrop toward the east. 
Section a— The eastern end of Section A, Atlas Sheet XXVI, is near 
the northern poimt of East Aspen Mountain, in granite. To the west the 
upturned beds of Cambrian and Silurian are successively crossed, then the 
Parting Quartzite and the Leadville dolomite. There are represented in 
this section the two faults into which the several breaks of the Ontario 
system have resolved themselves on East Aspen Mountain. Their position 
is not certain, but is approximately as shown, both having probably a 
slight downthrow on the west side. The blue limestone above the Contact 
fault actually outcrops, and above this comes the Silver fault, separating 
the porphyry from the blue limestone, with generally some little shale 
between. The Aspen fault is not well marked, but is shown as splitting off 
from the Silver fault and assuming a steeper dip at the point where the 
east limb of the syncline flattens to form its bottom, while the Silver 
fault continues across the syncline with the beds. The section cuts through 
the Homestake deep shaft and shows the large amount of drift which that 
shaft has traversed. This mound of drift is very conspicuous in the field, 
forming a low hill at the bottom of Vallejo Gulch. To one who is familiar 
with the landslides of the Rocky Mountains it is evident that this hill 
originated in some such catastrophe, and that Vallejo Gulch was cut 
through the material which formed this mound. The landslide took place 
in post-Glacial time, since the débris juts out into the valley, covering 
up the glacial materials. 
West of the Homestake shaft there are few opportunities for determin- 
iug the underlying rocks, and the structure is inferred from data gathered 
farther south. 
Section B—QOn the eastern side of Section B the beds flatten, indicating a 
tendency toward anticlinal structure. The two faults of the Ontario sys- 
tem are cut at a point farther south than in Section A. Their throw, there- 
fore, is greater. The flat dip on the top of the mountain steepens toward 
