334 University of California Publications. [Geology 



page 



First Epoch of Deformation of the Rosamond Series 360 



The First Cycle of Post-Miocene Erosion 361 



Volcanic Activity near the End of the First Cycle of Post-Miocene 



Erosion 366 



Deformation following Epoch of Volcanic Activity and Beginning a 



New Cycle of Post-Miocene Erosion 367 



Fault Scarps 369 



Rejuvenation 369 



Probable Antecedence of Black Canon 370 



Alluvial Slopes and Playas 371 



Composition, Texture, and Structure 371 



Origin of Materials and Processes of Formation 373 



Dissection and Canon-cutting in Alluvial Slopes 374 



Suggestions as to Correlation 378 



Summary ?. 380 



INTRODUCTION 



During the spring of 1911 the writer spent a period of two 

 months in the western half of the Mohave Desert and adjoining 

 areas for the purpose of collecting mammalian remains in the 

 fossiliferous formations recently reported to occur in that re- 

 gion. 1 In connection with this work it has been necessary to 

 make a geologic reconnaissance of the formations concerned, and 

 the following paper presents such results as it has been possible 

 to obtain in the progress of the work. The field work was 

 carried on in the interests of the department of palaeontology 

 of the University of California. Mr. Wallace Cordon, of the 

 University of California, assisted in the greater part of the field 

 operations, and Mr. John R. Suman, of the same University, 

 assisted in the examination of the Rosamond locality for the 

 purpose of making a petrographic study of the rocks of that 

 area. The author is also indebted to Mr. J. A. Sampson, Assist- 

 ant in Petrography in the University of California, for prelim- 

 inary determinations of rock specimens, and to Professor John 

 C. Merriam for the opportunity of undertaking the work and 

 for numerous suggestions during the progress of the field study 

 and the preparation of the report. 



i Merriam, J. C, A collection of mammalian remains from Tertiary 

 beds on the Mohave Desert. Univ. Calif. Publ., Bull. Dept. Geol., vol. 6, 

 pp. 163-169, pi. 29, 1911. 



