STUDIES FOR STUDENTS 425 



shows a fluvial deposit of one type in a stream terrace in north- 

 western Illinois. Lens and pocket structure is visible here. A 

 somewhat different type is shown in Fig. 3 , this being a photograph 

 of a section of an alluvial fan at the foot of the Sierra Nevada 

 Mountains in California. While these two deposits are quite 

 different, the differences are those of degree rather than of principle. 



Fig. 3. — ^A fluvial deposit at the foot of the Sierra Nevada Mountains in Ca]i- 

 fornia. 



CHARACTERS OF PLUVIAL DEPOSITS 



Pluvial deposits are similar to those deposited under fluvial 

 conditions, except that (i) the material is not so well sorted, (2) it 

 is more restricted in distribution, (3) the beds, if any, dip at higher 

 angles, (4) the material is more likely to be homogeneous litho- 

 logically, for it has not been transported so far from the parent 

 ledges, and (5), because not transported so far, the constituent 

 pieces are likely to be more angular. For the sake of easy reference, 

 the list of characters follows : 



1. Material coarse. 



2. High textural range. 



