96 GEOLOGY OF ASPEN MINING DISTRICT, COLORADO. 
been referred to in the case of the Justice fault, and therefore belongs 
to the Tourtelotte Park or postmineral system rather than to the Aspen 
Mountain or premineral system. Its greatest displacement is very close 
to the corresponding displacement in the Justice, being on the edge of 
the Tourtelotte basin. 
In this place it has an upthrow to the east of about 400 feet; but 
northward the throw diminishes with comparative rapidity. It is normally 
an upthrow to the east, but locally (see Section A, Tourtelotte special map, 
Atlas Sheet XIII) there is a downthrow to the east in consequence of 
faulting produced by the later east-west faults. Toward the north, also, 
the dip of the fault, which at the point of its maximum throw is appar- 
ently quite steep to the west, becomes progressively flatter, causing the 
approach of its outcrop toward that of the Justice fault, until, at the june- 
tion of Copper and Spar gulches, the two faults unite. It may be observed 
that for a considerable distance above the line of the junction of these two 
eulches the faults lie directly in the beds of the gulches and that the 
eulches themselves have been determined by the faults. As the Copper 
fault nears the point of junction with the Justice fault, the flattening of 
the dip of the fault combines with the decrease of the throw to cause the 
apparent displacement to become comparatively insignificant, so that at 
the point of junction with the Justice fault it has already nearly died out. 
South of the point where the fault has its maximum throw in Tourte- 
lotte Park there is the same phenomenon of swift diminution as in the case 
of the Justice. The Copper fault was not traced beyond the Butte fault, 
and probably does not continue very far beyond this point. 
Ontario fault The Ontario fault is so called because it hes at a point on 
the hillside a short distance above the Ontario tunnel, although it does not 
actually cut it. This fault has the same general characteristics as the Jus- 
tice and Copper faults, so that it has been classified with the Tourtelotte 
Park system rather than with the Aspen Mountain system. Like the Justice 
and Copper faults, it has a maximum throw in Tourtelotte Park, from which 
maximum it diminishes rapidly in both directions. Like these faults, also, 
its prevailing movement is a downthrow to the east; and like them it is 
younger in age than the ore deposition, and is therefore a postmineral fault. 
Tts maximum throw occurs about the middle of the area of the Tourtelotte - 
Park special map, bemg a downthrow to the east of about 1,00 ) feet (see 
