THE MESOZOIC OF SOUTHWESTERN OREGON 1 



GEORGE DAVIS LOUDERBACK 

 San Francisco, Cal. 



CONTENTS 



Introduction. 

 Historical. 

 Areas Studied. 



Present Knowledge of the Mezozoic of the Region. 

 The Myrtle formation. 



Outline of the Mesozoic and related history. 

 The Heterogeneity of the Myrtle Formation. 

 The Lithologic Characters of the Sedimentary Rocks. 

 The lower series. 



General composition. 



The sandstones. 



The shales. 



Conglomerates. 



Cherts. 



Limestone. 

 The upper group. 



General composition and comparison with lower series. 



Shales. 



Sandstones. 



Conglomerates. 

 Thickness of the Sediments. 



The upper division. 



The lower division. 



Paleontologic Characters. 

 The upper division. 

 The lower division. 



Terms Used. 



Definition of the Myrtle group or series. 

 The Dillard series. 



1 This study was made as research assistant of the Carnegie Institution of Wash- 

 ington, and is published by permission of the Institution. Read before the Cordilleran 

 Section of the Geological Society of America, December, 1904. 



Si4 • 



