912 



E. M. KINDLE CHARACTERISTICS OF MARINE CLASTICS 



have described^ from bed A of the Mount Wissick section in New Bruns- 

 wick an example of this kind which^ in the light of these experiments, 

 must be referred to continental or fresh-water conditions, although I 

 originally supposed it to have been formed on a tide fiat. 



Contrast in texture is another feature which may sometimes aid in dis- 

 criminating desiccated marine from fresh-water elastics composed of fine- 

 grained materials. The former show in many cases a vesicular and the 

 latter a compact non-vesicnlar texture. An interesting feature generally 

 shown by experimental desiccation of saline mud is the presence through- 

 out much of the material of numerous minute cavities. These cavities 

 were first noted in experimenting with the Pleistocene blue clay of the 

 Ottawa Valley, in which they had usually a diameter of from one-third 

 to one-half millimeter. Desiccated mud made with fresh water from the 



Air current ripple-mark 



Water current ripple-mark 



Wave ripple -mark 



Figure 7. — Diagrammatic Illustrations of Ripple-mark Types 



same clay showed no trace of the cavities, thus indicating that this feature 

 was due to the presence of the salt. This remarkable contrast between 

 the texture of desiccated mud containing salt and the texture of dried 

 mud free from salt was verified by a number of tests in which clay from 

 the bottom of Lake Ontario was used. In these tests duplicate lots of 

 mud were desiccated in vessels of the same size, the same quantity from 

 the same mixture being used in tlie parallel tests. The salt which was 

 added to one sample in each case was the only factor which was allowed 

 to differ in the two lots. In each case the dry saline mud showed numer- 

 ous small cavities which were absent in the corresponding sample of fresh- 

 water mud. Considerable geologic interest attaches to this feature be- 

 cause it is one which would in many cases almost certainly be preserved 

 permanently in the rocks. It should therefore furnish, in the case of 



Can. Geol. Survey, Mus. Bull. 2, 1914, p. 37. 



