BULLETIN OF THE GEOLOGICAL SOCIETY OF AMERICA 

 Vol. 2, pp. 49-74. January io, 1891. 



THE STRUCTURE OF A PORTION OF THE SIERRA 

 NEVADA OF CALIFORNIA. 



[Read before the Society December 29, 1890.) 

 BY GEO. F. BECKER. 



CONTENTS. 



Page. 



Summary of Observations 50 



Kegion studied 50 



Kocks and Exposures 50 



Fissures 50 



The Fissures are Fault Planes 51 



Frequency of the Fissures 51 



Age of the Fissures 51 



Absence of post-Glacial Faults 52 



Throw of the Faults 53 



Rules of Faults 54 



Inductive Examination of Dislocating Forces 54 



Relations of the Movements 54 



llorizontal Movements 55 



Resolution of Forces ^^ 55 



Analysis of a Thrust 56 



Result of a Thrust 59 



Conclusions as to horizontal Thrust 60 



Vertical movements 60 



Resolution of Forces 60 



What Forces are indicated 61 



A vertical Couple .-. 61 



Orientation of the Fissures 62 



Rotation 68 



Tilting of the Sierra 68 



Erosion of the Gravels 64 



Erosion influenced by Ice Cap 65 



Effects of the Fissures 67 



Effect of irregular Distribution 67 



Formation of Canons 68 



Formation of Domes 69 



VIII-BuLL. Geol. Soc. Am., Vol. 2, 18'JO. (49) 



