106 GEOLOGY OF ASPEN MINING DISTRICT, COLORADO. 
The folding had its maximum development in a line running approxi- 
mately parallel with this granite axis, and the movement was especially 
important in the upper beds, resulting in an overthrown, easterly dipping 
syneline, which had a slight pitch to the north. Judging, however, from 
the nature of this folding in the lower rocks, as now exposed by erosion in 
the southern part of the Tourtelotte Park special area, the amount of detor- 
mation is there not nearly so great; and it is probable that the fold became 
progressively less with depth and disappeared entirely in the granite. It 
has already been noted that with the increase in depth the overthrown, 
eastwardly dipping syneline tends to straighten up, and finally resolves 
itself into a normal open fold. To the west of this chief axis of folding 
there is a series of open folds, which, however, die away in a short distance, 
so that the beds become comparatively undisturbed. ‘To the east of this 
main axis, and between it and the granite, there existed a series of open 
folds, such as are now exposed by erosion in the Tourtelotte Park district, 
which were probably heavy in the upper strata, but all very gentle in the 
lower beds. 
2, The Silver system of faults —Synchronously with the folding, and as a result 
of it, there was a certain amount of slipping of one bed over another to 
accommodate themselves to the new position into which they were forced. 
This gave rise to fault zones or fault planes nearly or quite coincident with 
the bedding, which, however, have great persistence and a notable amount 
of displacement, and have played an important part in the economic his- 
tory of the region. These faults are very numerous throughout the whole 
district, but two of them are perhaps more important in the study of ore 
deposition than any two other faults which may be found. One of these, 
which has been called the Contact fault, appears to be strictly parallel with 
the bedding, at the contact between the blue foraminiferal limestone and 
the underlying dolomite of the Leadville formation. Its displacement, 
therefore, can not be measured, but that it has been considerable is proved 
by the slickensiding and brecciation almost always found along it. The 
other fault is also very nearly parallel to the bedding, but frequently cuts 
it at a very slight angle, so that portions of the strata are carried away by 
its action in certain localities. The amount to which the strata have thus 
locally been cut down shows that the movement along the fault has been 
very great. 
