422 STUDIES FOR STUDENTS 



at least this is not a happy division, for after analysis it is clear 

 that the differences between deposits above low-water mark and 

 those below low-water mark are slight, and that the differences 

 between deposits in greatly agitated waters and those in quieter 

 waters are great. In spite of infeHcities of expression, it seems 

 best here to divide the shallow-water deposits of the sea into two 

 groups, (a) those of the zone of major agitation, and (b) those of 

 the zone of minor agitation. The deposits of the zone of major 

 agitation include beach deposits, bars, spits, hooks, barrier reefs, 

 etc., for the most part materials laid within the surf line, and the 

 deposits of minor agitation are those laid in quieter water in general 

 beyond the surf line. None of the other terms needs definition here. 

 The lists of characters of these various sorts of deposits, given 

 below, are the results of (i) a study of the processes and agents by 

 which they are deposited, and (2) observation of undoubted types 

 of the various sorts of deposits in the field. Sand dunes have been 

 studied at the south end of Lake Michigan and loess in Iowa, 

 IlHnois, and Wisconsin. Fluvial deposits were examined par- 

 ticularly in Owens Valley, California. Pluvial deposits were noted 

 in Owens Valley, and in the southern Appalachians; talus slopes 

 in Wisconsin, California, and Wyoming; glacial materials in Wis- 

 consin and Illinois; lacustrine deposits in extinct lake bottoms in 

 Wisconsin, and in the Pliocene lake deposits of the Inyo Mountains; 

 and marine deposits in the Paleozoic rocks of the Mississippi 

 Valley. 



CHARACTERS OF EOLIAN DEPOSITS 



Eolian deposits have the following characteristics. For the 

 sake of brevity they are listed. 



1. Low textural range. 



2. Material all finely divided. 



3. Sorted into irregular beds and lenses. 



4. Stratification-planes dip in all directions. 



5. Stratification-planes have dips varying in amount up to 30° ±. 



6. Material porous. 



7. Distributed in irregular areas, not continuous. 



8. Vary greatly in thickness within short distances. 



9. May be ripple-marked. 



10. Grains of sand are rounded. 



11. Fossils, if any, are of terrestrial forms. 



