ASPEN DISTRICT MAP. 133 
Mountain, which causes the outcrop of the sedimentary beds to advance 
to the west. The north-south faults of the Aspen system are shown dying 
out under the valley of the Roaring Fork. The exact point at which 
these die out is, of course, not known, and they may extend farther into 
the Maroon formation than has been represented; but in this formation 
there is no means of tracing their extension, on account of the similarity of 
the beds on either side. 
This joming of the several maps brings out more clearly the salient 
features in the structural geology of the district. As one looks at the map 
and observes the comparatively narrow zone along which outcrop the beds 
lying below the Maroon and above the basal granite, the most distinctive 
feature is the contrast between that part of the belt north of the town of 
Aspen and that part to the south. Throughout the Hunter Creek district 
the beds maintain comparatively uniform strike and dip, and are not broken 
to any extent by cross faulting. Southwest from this there comes in a 
remarkable change at the town of Aspen, which is marked by the sudden 
advance of the outcrops toward the west, by the change in the strike of 
the beds from northeast to nearly north, and by the beginning of a series 
of important and complicated faults. All these disturbances appear very 
suddenly, and may be said to be centralized in the northern part of the 
area of the Tourtelotte Park special map. The sudden advance of the out- 
crops toward the west is due to the presence of the uplifted dome, which 
apparently has its highest point in the northern part of Tourtelotte Park, 
but has a steep face toward the north, so that it is practically wanting in 
the Roaring Fork Valley. The change in the strike of the beds has no 
apparent connection with this extremely local uplift. If one regards, how- 
ever, the general line of contact between the granite and the overlying 
beds from the northern part of the Hunter Creek area to the southern edge 
of the district, it will be seen that this outcrop forms a single large curve. 
Along this line the beds have a uniform dip away from the granite, except 
where, as in the Tourtelotte Park area, this dip has been locally altered. 
It may be, therefore, that all these beds are lying upon the flanks of an 
uplifted dome, which was larger and had a more uniform and a gentler 
uplift than had the more concentrated disturbance in Tourtelotte Park, and 
that the Tourtelotte Park uplift was but a smaller and comparatively more 
violent manifestation of the same uplifting force which caused the larger 
