BULLETIN OF THE GEOLOGICAL SOCIETY OF AMERICA 

 Vol. 28, pp. 917-924 DECEMBER 19. 1917 



CHARACTERISTICS OF CONTHSTENTAL CLASTICS AND 

 CHEMICAL DEPOSITS ^ 



BY ELIOT BLACKWELDER 



{Presented before the Society December 29, 1916) 



CONTENTS 



Page 



Entroductiou 917 



Determining factors 918 



Climatic types of sediments 920 



Classification 920 



Pure or extreme types 920 



Sub-Arctic type 920 



• Humid, tropical type 921 



Desert type 921 



Mixed types ' 922 



Intermediate types 923 



Need of exact data ' 924 



Introduotion" 



Broadly considered, the continental sediments are all those which have 

 been deposited elsewhere than in the sea. By this definition we must in- 

 clude among them not only the deposits made by rivers and other agencies 

 working on the land, but also the sediments laid down in lakes and 

 marshes. Between marine and continental types there is, of course, no 

 sharp line of demarkation, but a transition zone occupied by the deposits 

 made in estuaries, tidal lagoons, and sounds, on beaches, deltas, etcetera. 



It would be gratifying if we could establish a few simple rules for dis- 

 tinguishing between marine and continental deposits; but with certain 

 exceptions this is impracticable. There are but few satisfactory criteria 

 of general applicatio]j for separating continental from marine sediments. 



In the past reliance has often been placed on the fossils; but in the 

 continental sediments fossils are generally wanting, and not uncommonly 



1 The foLU-th of a series of papers composing- a "Symposium on the Interpretation of 

 Sedimentary Roclis." This brevity of treatment is due to the fact that the time for 

 presentation was limited to ten minutes. 



Manuscript received by the Secretary of the Society March 24, 1917. 



(917) 



