BULLETIN OF THE GEOLOGICAL SOCIETY OF AMERICA 



Vol. 28, pp. 925-932 DECEMBER 19, 1917 



SIGNIFICANCE OF SORTING IN SEDIMENTAEY ROCKS ' 



BY EUGENE WESLEY SHAW 



{PresenieA before the Society Deceinher 20, 10 U>) 



CONTENTS 



Page 



Dominant considerations and tlie question raised , 925 



The factors affecting sorting 926 



Note on previous workers 927 



Methods of making analyses. 927 



Methods of studying analyses 927 



Sizes of grains in separates 928 



Significant features of diagrams 928 



Possibility of other significant features being found 929 



Fundamental cause of sorting 930 



"Monograms" of various kinds of deposits 931 



Conclusion 931 



Dominant Consideeations and the Question Raised 



The facts that the grains composing most sedimentary rocks show more 

 or less sorting, that this sorting is not uniform, either in degree or kind, 

 and that the rocks are known to have been laid down by various agents, 

 naturally leads to the question : To what extent may it be possible to de- 

 termine, from the mechanical constitution of a layer of sedimentary rock, 

 what conditions and processes affected its deposition? The term sedi- 

 mentary rock is here used in preference to clastic rock, for not only dn 

 most deposits which were once sediments show some sorting, but the 

 grains composing many of the so-called chemical deposits, particularly the 

 limestones, seem to have been transported and sized to a greater exteni 

 than generally realized. One is deeply impressed with this fact, particu- 

 larly when observing the sea bottom in diving apparatus. The lime-de- 



iThe fifth of a series of papers composing a "Symposium on the Interpretation ol' 

 Sedimentary Rocks." 



Manuscript received by the Secretary of the Society May 15, 1917. 

 Published l)y permission of the Director of the U. S. Geological Survey. 



(925) 



