BULLETIN OF THE GEOLOGICAL SOCIETY OF AMERICA 

 Vol. 21, pp. 543-564 October '12, 1910 



EELATIONS OF PEESENT PEOFILES AND GEOLOGIC 

 STEUCTUEES IN DESEET EANGES^ 



BY CHARLES R. KEYES 



{Presented hy title before the Society December 29, 1908) 



CONTENTS 



Page 



Introductory 543 



Subdivisions of the American arid region 544 



Explanations of the origin of the Great Basin ranges 545 



General tectonics of the desert region 546 



Naturie of the younger tectonics 547 



Character of the older tectonics 548 



General features 548 



Older geologic structures of the Great Basin region 549 



Types of ancient structures of the Basin ranges 550 



Older geologic structures of the Colorado Plateau province 555 



Older geologic structures of Californian Gulf basin 555 



Older geologic structures of the Mexican tableland 556 



Relations of the mountain ranges to flexures 559 



Geologic evolution of desert ranges 559 



Recapitulation 563 



Introductory 



Mountains of the so-called Basin-range type occur over a very much 

 larger area of western America than is commonly supposed. They not 

 only occupy the Great Basin country, but an expanse of territory ten 

 times as vast. The desert ranges extend from the northern boundary ol 

 the United States southward far into Mexico. Throughout this great 

 area they preserve intact all of their distinctive characteristics : more or 

 less complete isolation of the ranges, abrupt elevation above the sur- 

 rounding plains, lofty heights, short lengths, simplicity of structure, and 

 the very resistant nature of their rocks. There are many other equally 

 distinctive features which are not so conspicuous. 



Manuscript received by the Secretary of the Society December 31, 1908. 



(543; 



