UNIVERSITY OF CALIFORNIA PUBLICATIONS 



BULLETIN OF THE DEPARTMENT OF 



GEOLOGY 



Vol. 10, No. 21, pp. 383-420, 4 text-figs., pis. 28-33 November 27, 1917 



THE BRECCIAS OF THE MARIPOSA FORMATION 

 IN THE VICINITY OF COLFAX, CALIFORNIA 



BY 



CLARENCE L. MOODY 

 CONTENTS 



PAGE 



Introduction 383 



Location and topography 384 



General geology 386 



Stratigraphy of the Mariposa formation 388 



General statement 388 



Slate ._ 389 



Sandstone 390 



Breccia 391 



Occurrence .' 391 



Megascopic features * 394 



Microscopic features 397 



Breccias in other areas of the Mariposa ■. 397 



Palaeontologic evidence 398 



Classification of related conglomerates 399 



General statement 399 



Marine 400 



Fluviatile 401 



Glacial 402 



Fanglomerates '. 405 



Probable origin of the Breccia 406 



Structure 410 



Igneous rocks in the Mariposa 413 



Resume 413 



INTRODUCTION 



The Mariposa formation, which has long interested students of the 

 Sierra Nevada, is exceptionally well exposed in the vicinity of Colfax ; 

 it is believed that a more favorable locality for the study of its 

 stratigraphy will not be found. 



