902 GEOLOGY 



Jersey, this member of the Columbia series is called the Cape May 

 formation. Fig. 594 shows, diagrammatically, the supposed rela- 

 tions of the three phases along an interfluvial tract, from the c< > 

 inland. 



The various members of the Columbia series rest unconformably 

 on older formations. On the Atlantic Coast, the older divisions 

 often rest on the Lafayette formation, and often on terranes from 

 which the Lafayette had been eroded before the deposition of the 

 Columbia series (Fig. 595). 



Fossils. The Columbia series rarely contains fossils; but at a 

 few points shells of fresh-water mollusks have been found in the 

 Pensauken a few feet above sea-level. Marine shells have been 



Fig. 594. Diagram showing the theoretic relations of the three principal 

 subdivisions of the Pleistocene outside the valleys, along a line normal 

 to the coast. The letters have the same significance as in Fig. 593. 



found in gravels which are perhaps of Pensauken age, on the east 

 coast of New Jersey. Such evidence as the few fossils afford, 

 therefore, is against the marine origin of at least parts of the forma- 

 tion. The Cape May formation, like the older Pleistocene forma- 

 tions of the Atlantic Coast, is generally without fossils, but marine 

 shells have been found in it at a few points (southern New Jer- 

 a few feet (10 or less) above sea-level. 



The origin of the Columbia and associated formations. The 

 origin of the Columbia formation presents much the same problems 

 as that of the Lafayette, and is probably to be explained in much 

 the same way; that is, the series is looked upon as largely sul>;i<Tial 

 (pluvial and fluvial), the result of land aggradation. The occasion 

 for renewed deposition on the Coastal Plain in the Quaternary 

 period probably lay (1) partly in changes of gradient incideir 

 surface warpings, and (2) partly in the changes of climate <>f the 

 period. Slight further upward bowing of the highlands v. 

 the coast probably stimulated the streams desrendin; from them 



