THE DISTRIBUTION OF LOESS FOSSILS 



It has perhaps been noted that the loess molluscs thus far 

 reported in the literature of the subject are, for the most part, 

 from localities in close proximity to the larger streams. This 

 fact may have suggested the thought to those unfamiliar with 

 the modern habits and present distribution of these molluscs 

 that the adjacent streams had in some way something to do with 

 the entombing of the shells now found in the loess. That the 

 loess is most richly fossiliferous near streams is generally, though 

 not always, true. The abundance of fossils is a decidedly vari- 

 able quantity. There are exposures near streams which exhibit 

 fossils in profusion, and others which are wholly barren. On the 

 other hand, exposures quite remote from streams contain fossils 

 — though in such situations a proportionately much larger part 

 of the loess is entirely devoid of them. 



This fact has sometimes led geologists to attempt to distin- 

 guish, in varying degrees, between the loess adjacent to streams 

 and loess more remote. Whatsoever distinction may be observed 

 in the physical characters of the loess of various deposits, 1 no 

 distinction can be based on the presence or absence of fossils 

 alone. The simple fact that one deposit is fossiliferous and 

 another is not, does not prove, nor even indicate, that the depos- 

 its were formed under wholly, or even materially different cir- 

 cumstances. In the one case there are no fossils simply because 

 there were no shells to be buried ; in the other, fossils are com- 

 mon because shells were abundant on the old land surfaces, 

 where they were covered as other imperishable objects would 

 have been covered. 



Fossils are more abundant in the vicinity of streams because 



*For one of the most recent discussions of the loess with reference to its variation 

 according to distance from streams, see Dr. Chamberlin's article in the Jour. Geol., 

 Vol. V, No. 8, p. 795. 



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