25 



Bridgeton. Indeed, it seems that the successive Pleistocene submer- 

 gences of this State became slighter and the glacial influence less 

 pronounced as the Recent period was approached. 



PENNSYLVANIA AND DELAWARE. 



The extreme eastern border of Pennsylvania along the Delaware, 

 south of Trenton, has surficial deposits of Pleistocene corresponding 

 to the Pensauken and Cape May of New Jersey, just across the 

 river. Delaware, lying between New Jersey and Pennsylvania on 

 the one hand and Maryland on the other, is largely covered with the 

 Pleistocene. The divisions of the Pleistocene in Maryland corre- 

 spond to those in New Jersey ; and the Delaware Pleistocene, though 

 almost no recent work has been done on it, is undoubtedly capable 

 of being divided in the same way. 



MARYLAND. 



The Pleistocene in Maryland consists of a mantle of unconsoli- 

 dated loams, sands and gravels, covering most of the earlier deposits 

 of the lowland and lapping well up on the Piedmont Plateau in 

 places. McGee, Darton, Shattuck and others have worked on the 

 relationships between the different phases of the Pleistocene and 

 earlier formations. The Columbia or Pleistocene has been divided 

 variously by the different workers in the field. One division makes 

 a fluvial and an interfluvial phase, together with a littoral or low- 

 level deposit. The fluvial consists of deltas deposited under water by 

 those streams in whose valleys they now occur when the land stood 

 lower than it does today. It is subject to further division, the lower 

 member being composed of sand, gravel and huge bowlders, the 

 upper of clay and loam. The material as a whole is coarser near the 

 mouths of gorges, where the streams leave the Piedmont Plateau, 

 than in the more remote parts of the deltas. The interfluvial phase 

 possesses no regular stratification, but is an indiscriminate mixture of 

 clay, sand and gravel, water fashioned but not fluvial, which mantles 

 the divides. The low-level deposit, just along the shore and in some 

 cases extending up the rivers, contains in some of its exposures fos- 

 sils of mollusca and other forms. Another division, that of Darton, 

 separates the Columbia into an earlier and a later Columbia. The 

 Columbia rests unconformably upon the Lafayette or Pliocene. 

 These three formations, the Lafayette and the two members of the 

 Columbia, are found in the upper part of the stream channels which 



