UTAH ACADEMY OF SCIENCES 159 
MID-TERTIARY DEFORMATION OF WESTERN 
NORTH AMERICA. 
BY HYRUM SCHNEIDER. 
(Abstract). 
It is quite generally conceded {that the Tertiary 
period in North America was ushered in by a marked 
deformation most conspicuous in the Rocky Mountain 
region and was ushered out by another deformation 
which probably affected to some extent most of North 
America, but in its more marked features was confined 
to the Pacific Coast. Somewhere near the middle of the 
Tertiary there was a deformation somewhat analogous 
to the opening and closing disturbances. 
The problems of this thesis are an investigation of 
the middle Tertiary deformation:—(a) To locate it as 
nearly as possible in time; (b) To investigate its nature 
and extent; (c) To determine some of its effects; (d) 
To study its relation to Mid-Tertiary deformations in 
other parts of the world. 
As shown by structure sections there began in Wes- 
tern North America, near middle Miocene time, a period 
of disturbance which affected profoundly the Pacific 
Coast region from Southern California to Puget Sound 
and probably extended along the coast to Northern 
Alaska. From Southern California it probably extended 
south to Central America. Passing east from California 
the Great Basin was markedly affected and the distur- 
bance practically died out in the Great Plains east of 
the Rocky Mountains. 
The Coast Ranges, part of the Cascade Range, the 
Olympic Mountains, and a part of Alaska were closely 
folded. In the Coast Ranges horizontal thrust faulting 
accompanied the folding. At least a part of Alaska, the 
Coos Bay region of Oregon, the John Day Basin of Ore- 
gon and the Western part of the Great Basin were moder- 
