Geology of Ft. Apache Region, Ariz. — Reagan. 293 
Diverting of Drainage by faulting, and consequent laking. 
— Before the deposition of the Tertiary the region was much 
faulted and tilted so that it was laked. At first only two small 
lakes were formed : one in the canyon of the then master stream 
southeast of Fort Apache, the other between the Pinal-Sierra 
Ancha mountains and the Plateau-Canyon creek escarpment, 
in the area through which Salt river now runs. As soon as the 
faulting began the head-streams began to adjust themselves to 
the new conditions, each cutting out a channel in its lower 
course along a north and south fault to the main east and west 
fault line now occupied by Black-Salt river. At first the waters 
of some of the streams flowed east along this fault to the east- 
ern lake, the waters of the other streams west to the western 
lake. Finally, as the region became more elevated on the east 
the eastern lake drained west along the major fault into the 
western lake which in turn drained south between the Apache 
and Pinal mountains into the Gila river via Pinal Creek canyon. 
After the drainage had continued in this direction for a consid- 
erable time a further elevation of the Plateau-Canyon creek 
escarpment blocked the drainage to the west and made a lake 
of the entire Black-Salt river basin east of that escarpment, the 
western lake remaining practically unchanged and still having 
its outlet via Pinal Creek canyon to the Gila. 
The sedimentation due to the laking of the region has al- 
ready been discussed under Tertiary and Quaternary deposits 
in the remarks on the Stratigraphy of the region, and need not 
be further mentioned here. 
Destruction of Lakes and the present Salt river Drainage. 
— Near the close of the Quaternary, Salt river re-cut its chan- 
nel through the elevated plateau-escarpment emptying into the 
western or Hinton lake. At about this time a channel was cut 
through between the Sierra Ancha and Pinal mountains, giving 
Salt river the channel it occupies today in that part of the re- 
gion. Since cutting the outlet, Salt river and its tributaries in 
their lower courses have incised themselves to the depth of 
about 2000 feet. 
As the process of degrading went on several geographical 
accidents happened to several of the streams. White river and 
its North Fork, for example, cut a deep channel, where they 
now run in the Cretaceous and were subsequently laked and 
