8 Quaternary Formations of Southern New Jersey. 



Complications. — The above illustration embodies the essential 

 principles involved in the development of the Quaternary forma- 

 tions of this region, as here interpreted; but the real case is com- 

 plicated by the fact that the bases on which the several forma- 

 tions, corresponding in a general way to i, 2 and 3, were de- 

 posited, were not plane, and the deposition of the several forma- 

 tions on uneven surfaces complicates their topographic relations. 

 If, for example, the surface beneath formation 1, Fig. 1, were 

 irregular, that formation might, in the depressions of its base, 

 reach a level as low as that attained by the higher parts of 

 formation 2. In this case, there would be no* certain way of 

 discriminating between 1 and 2, on topographic grounds alone, 

 after erosion has proceeded so far that isolated remnants only of 

 the two formations remain. Corresponding relations might hold 

 between formations 2 and 3. These relations, as a matter of fact, 

 exist. 



There is still another complication from the topographic point 

 of view. Thus, while formation 2 was being laid down in the 

 main valley, the corresponding deposits made in a tributary valley 

 rose to higher and higher levels, as the source of the tributary 

 was approached. At the proper distance from the main stream, 

 these deposits in the side valley may have risen to the level of 

 formation 1. Similarly, the deposits made in the valleys of the 

 side streams, while formation 3 was being laid down in the main 

 valley, rise upstream, and, at the proper distance, may reach the 

 level of formation 2 in that valley, or even of formation i.- 



Application to New Jersey. — The Bridgeton formation is illus- 

 trated by No. 1 above, the Pensauken formation by No. 2, and 

 the Cape May formation by No. 3. 



It follows ( 1 ) that the borders of the Quaternary formations 

 of this region are not denned by contour lines, though the forma- 

 tions are not independent either of topography or drainage ; and 

 (2) that, while there are principal stages of deposition, there are 

 also deposits made at all intermediate stages. If three forma- 

 tions be recognized, corresponding with three principal stages of 

 deposition, it is, nevertheless, impracticable, in some cases, to say 

 with certainty whether a given deposit belongs to one of these 



