568 PRINCIPLES OF STRATIGRAPHY 



primary distribution and deposition of loess, for loess is forming to- 

 day in China and Central Asia, and in many other regions of the 

 world.* 



Fossils and concretions in the loess. The fossils of the loess are 

 few and found only at intervals. They are for the most part shells 

 of land snails (Helix, Pupa, Succinea) and of pond and stagnant 

 water types (Planorbis, Paludina, etc.). Bones of land vertebrates 

 are, however, not uncommon in many loessial deposits, while stems 

 and roots of grasses and other plants, more or less replaced or 

 mineralized, are characteristic features in certain regions, espe- 

 cially in China. Curiously formed calcareous concretions known as 

 Locssvi'dnnchcn, Loesspilppchen, or Loesskindel are also found in 

 many deposits of loess. These often occur in horizontal tiers, giv- 

 ing a semblance of stratification to the deposit. They are, however, 

 of secondary origin, and the arrangement is not necessarily indica- 

 tive of original stratification, but may represent successive levels of 

 ground water. An analysis of the concretions of the German loess 

 gave (Blanck-5) : 



SiOa 34- 824 MgCOs 1.890 



AI2O3 \ K2O 1.048 



FeoOs J 4""^ NaoO 1.202 



CaO 0.203 P2O5 0.157 



CaCOs 55-294 SO3 0.090 



MgO 0.178 HoO 0.377 



Cenozoic and Mesozoic Loess-like Deposits. Deposits of this 

 type are probably more widespread than is realized at present. The 

 White River clays of Oligocenic age in western North America 

 have been regarded by W. D. Matthew (31) as probably of this 

 type, though the included sandstones are in part at least fluviatile 

 and in part perhaps dune sands. The chief characters stamping 

 these deposits as eolian loess are the fineness of their texture, the 

 lack of stratification and the absence of plants, fish or aquatic rep- 

 tiles or invertebrates, as well as the larger number of land mam- 

 mals. All of these characters are incompatible with the theory of a 

 lacustrine origin of these deposits commonly held for them. A loess- 

 like origin has also been suggested for the Harrison beds of Ne- 

 braska, a Aliocenic formation. (Loomis-30 ://.) Anemolutytes 

 comparable to the modern loess seem to be represented by the 

 Keuper marls of western Europe. These have been regarded as the 

 loessic deposits formed around the borders of the Triassic desert, 



* For a comprehensive bibliography of the loess see Stuntz and Free (50) 

 pp. 124-140. 



