ulrich: major causes ok oscillations 63 



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of sea level could have been eustatic. On the reversal of this 

 sea level movement, when the Pleistocene ice sheet stretched to 

 the shore and when as stated above, the consequent bulj^inj; of 

 adjacent parts of the continental shelf reduced the capacity of the 

 ocean basin, the change in sea level as manifested in the advance.' 

 and retreat of the Atlantic shore north of, say Cape Hatteras, 

 was far from eustatic. During this maximum extent of the 

 Labrador ice sheet, the ice-covered near-shore lands about the 

 Gulf of vSt. Lawrence must have sustained extensive submergence. 

 Southwardly from northern Maine to New Jersey the amount- 

 of this submergence decreased perhaps to its minimum. On 

 the other hand, in Maryland, which I take to have lain at thai 

 time within the belt of peripheral isostatic elevation, the land 

 was pushed up with resultant apparent or relative sinking of sea 

 level. Farther south, beyond the belt of peripheral bulging, the 

 Atlantic shore probably shared in the ( ustatic rise of sea level 

 that prevailed generally because of the temporarily decreased 

 capacity of ocean basins except in the areas affected immediately 

 and differentially by the ice sheets. 



Correlation of Pleistocene sea beaches in Maryland and Maine 

 therefore suggests and perhaps requires comparison oT the high 

 beaches in Maryland with low beaches in New England. 



Because of this dissimilarity in manifestation, it seems to me 

 that it is only in the warm temperate and tropical zones lying 

 well beyond the areas in which isostatic balance would be ma- 

 terially disturbed by known ice loading of lands, that the sequence 

 and amount of the several glacially controlled Pleistocene changes 

 of sea level are recorded in their proper relations to the actual 

 fluctuations of the volume of sea water and to the capacity 

 variations of the basins holding it. But even in tropical areas 

 the complete sequence of the oscillations and the immediate 

 cause of each cannot be worked out without taking strict ac- 

 count of what was happening at the same times in higher lati- 

 tudes.. 



In thinking of the progressive and regressive sequences of move- 

 ments it is well to remember that ice loading and sediment 

 (rock) loading of epicontinental areas are comparable in their 



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