Theory of Formation of Sedimentary Deposits. 123 



by an oldland area whether it be a region of metamor- 

 phosed rocks, such as we find in the great Archean areas 

 of Canada, or by an oldland area consisting of sediments 

 deposited at some preceding time, but subsequently 

 uplifted. In this latter case there may be temporary 

 irregularities in the supply of material for any one 

 or two of the different zones, and it is quite probable 

 that the coarser material in its (n + l)th. transporta- 

 tion, assuming that the sedimentary beds supplying 

 it represent the nth series of beds of which it has 

 formed a part, will be in a somewhat finer state of 

 division. Hence that material which in the nth series of 

 sedimentaries occurs in the shore zone, may in the 

 (n + T)th series be found in part, at least, in the two 

 outer zones. Quite frequently also, material derived from 

 beds formed in a preceding cycle of deposition will retain, 

 in its new position, certain characteristics (of color, form, 

 structure, content) which make it possible to recognize 

 that it belonged to a preceding cycle of sedimentation. 

 On the other hand, it will often lose these characteristics, 

 and then it will be impossible to infer the number of cycles 

 of sedimentation through which it has passed to its present 

 resting place. 



Directly or indirectly, the materials which go to form 

 the sub-aqueous deposits are derived chiefly from the 

 waste of the land. In the case of the limestones of various 

 types and, in part, of some of the shales, the material of 

 which they are composed is less often a direct derivative of 

 the waste of the oldland, more frequently it is a secondary 

 product due to the intervention of organic life or to 

 chemical action. In the previous discussion reference 

 was made to the normal existence of a zone in which 

 limestone would be formed. When we consider the usual 

 manner of the formation of this limestone it became 

 necessary to modify, to a certain extent, our primary 

 theoretical concept. Along the margin of the land within 

 the zones of deposition of sands and shales, the materials 



