1904.] HATCHER — MARINE AND NON-^L\RINE FORMATIONS. 347 



the thickness of the various deposits forming in this region. More- 

 over, if the elevation to the westward should become appreciably 

 more rapid than to the east the run-off would be increased by the 

 greater inclination of the surface toward the sea, and a period of 

 erosion would be inaugurated over a considerable portion of that 

 area where formerly fresh water deposits were being formed. 



If on the other hand the region should undergo a general but 

 gradual subsidence, so gradual that the rate of upbuilding by depo- 

 sition would be more than sufficient to keep pace with the subsidence, 

 the result would be a lengthening of the time necessary for the coast 

 line to advance eastward from its present position to that of the 

 easiern border of the continental plateau and a corresponding 

 increase in the thickness of the various deposits. Under such con- 

 ditions the thickness of the littoral and estuarine or brackish water 

 deposits would not be so restricted as under those conditions pre- 

 viously considered, but these might attain to almost any depth, 

 varying in thickness at any given point according to whether the 

 rate of subsidence during the deposition of these deposits at such 

 point approximated or fell far below the rate of sedimentation tak- 

 ing place there. The more nearly the rate of subsidence approxi- 

 mated that of sedimentation at any point where littoral and brackish 

 water conditions prevailed, the greater would be the length of time 

 necessary to recover the area from the sea and the greater the thick- 

 ness of the littoral and brackish water deposits. 



If at any time the rate of subsidence exceeded that of sedimen- 

 tation, conditions would immediately be reversed, the sea would 

 encroach upon the land, the coast line would recede to the west- 

 ward, and the fresh water beds seen at No. 4 in the diagram would 

 be overlaid first by a brackish water deposit, over which would be 

 laid down a littoral deposit, followed later by beds of deep water 

 origin as the subsidence increased and the sea advanced upon the 

 landt If this period of more rapid subsidence were only temporary 

 it would result merely in a local interstratification of fresh water, 

 brackish and marine deposits. If on the other hand it became 

 permanent it would result in the entire resubmergence of the region 

 already recovered from the sea, and there would be a repetition in 

 reversed order of the fresh water, brackish, littoral and true marine 

 deposits already described as having been formed during that 

 period when the land was advancing upon the sea. At the close of 

 his period of subsidence, when the sea had regained its original 



