EOLIAN DEPOSITS 551 



The various types of wind-deposited rock material or anemo- 

 liths may, then, be grouped as follows : 



Endogenetic Exogenetic 



(non clastic) (clastic) 



A nemoliths A nemolilhs 



Pyroclastic 

 Autoclastic 

 Atmoclastic 



1 . Pyrogenic I 



2. Atmogenic 2 



3. Hydrogenic 3 



4. Biogenic 4 



a. Zoogenic 5 



b. Phytogenic 6 



Anemoclastic 

 Hydroclastic 

 Bioclastic 



The term anemolith in this case refers to deposition by wind, 

 while the origin of the material is indicated by the qualifying term. 

 The immediate sources of the material for sand dunes are the beach 

 sands of sea and lake, the flood plains and terraces of rivers, gla- 

 cial deposits and disintegrating rocks of the region. The dunes of 

 our coast are largely fed by the beach sands. River terraces and 

 flood plains furnish much of the material for the dunes of river 

 valleys, while glacial sands sometimes directly furnish material for 

 dunes, as on the uplands of Cape Cod, and in the North German 

 lowlands. Desert dunes may be derived from disintegrating sand- 

 stones, as in the case of the Libyan and Nebraskan dunes, or from 

 the flood plains of rivers, as in the case of the Kizil Kum and 

 Kara Kum of the Transcaspian deserts. Dry lake bottoms may also 

 form a temporary source of eolian material. 



Textural Types of Anemoliths. 



Two textural types of anemoliths may be recognized, anemo- 

 lutytcs or dust deposits and ancmoarcnytcs or eolian sand-dune de- 

 posits. Anemolutytes will, as a rule, show no, or but little, dis- 

 cernible bedding structure, and this may also be true of the fine 

 grades of anemoarenytes. The loess may be taken as a typical ex- 

 ample of this kind of deposit. Eolian sands (anemoarenytes), es- 

 pecially the coarse types, commonly accumulate in the form of sand 

 dunes, and these will show a typical dune-bedding structure. This 

 is also true of biogenic and atmogenic anemoliths. 



General Characteristics of Modern Eolian Deposits. 



The chief characters of eolian deposits are their thorough 

 sorting, according to size of grain and mineral material, the round- 



