160 TRANSACTIONS OF THE 
ately folded. In the western part of the Great Basin 
folding was probably: accompanied by faulting on a 
large scale. The Sierra Nevada Mountains were up- 
lifted bodily without folding. The eastern part of the 
Great Basin and the Rocky Mountain region were up- 
lifted and locally faulted. 
In the Pacific Coast region the disturbance was most 
pronounced with consequently more diverse effects. 
Submerged areas were elvated thousands of feet above 
sea level while other areas were submerged. In general 
there was a marked increase in relief and a new active 
cycle of erosion was begun. 
In the Great Basin and Rocky Mountain region the 
disturbance probably began ‘the (development of the 
major topographic features of today. 
While the main problem of this thesis deals with 
the Mid-Tertiary deformation of Western North Amer- 
ica, the disturbance was by no means limited to North 
America. It is, for the world as a whole one of the most 
profound and extensive recorded in geologic history. 
That its effects have not yet entirely died out is strongly 
suggested by the close relationship between the area 
affected and the present distribution of active or rela- 
tively recently active volcanoes. Also the area most 
frequently affected by earthquakes is closely related to 
that portion of the world most affected by the Mid-Ter- 
tiary disturbance. 
