Introduction — Principles Involved. 3 



of the Coastal Plain farther south, which were described 

 formerly under the omnibus name Columbia formation. These 

 beds really constitute a series, rather than a single formation, 

 and the term Columbia will be used here to cover the series as a 

 whole, separate names being applied to its several principal mem- 

 bers. The divisions of the Quaternary here recognized are three 

 in number. In order of age, they are (1) the Bridgetcw forma- 

 tion, (2) the Pensauken formation, and (3) the Cape May for- 

 mation. 



Origin. — Various views concerning the origin of these forma- 

 tions have been held by -those who have studied them, and this 

 diversity of interpretation still exists. (1) Some have thought 

 them to be of marine origin, and to represent successive sub- 

 mergences of the southern part of the State up to heights marked 

 by their upper limits, the several submergences being separated 

 by emergences. (2) Others have thought the several forma- 

 tions to be of subaerial origin, that is, deposited on land, chiefly 

 by running water. (3) Still others have thought the forma- 

 tions in question to be partly of subaerial, and partly of marine 

 or estuarine origin. Within the last view, opinion has varied as 

 to the proportion of the series to be assigned to the one origin 

 or to the other. The third view is the one here favored, with 

 emphasis on the- subaerial, rather than on the marine or estuarine 

 mode of origin. 



The broad question of subaerial accumulation of sediment is 

 one which, until recently, was neglected; but within the last 

 decade or two, recognition of its importance has become general. 

 Deposition of sediments on land is now in progress at the bases 

 of most slopes, and about most high lands, and it is not easy to 

 see how similar results can have failed of realization under 

 similar conditions of climate and topography, at any time in the 

 past. Deposition is effected not merely by rivers which lead 

 from mountains to plains, but by the run-off of every shower 

 which descends from one slope to another of lesser grade or to a 

 flat. The effectiveness of the process and the extent to which 

 sediments may be spread over the surface where conditions are 

 favorable, is best shown on the plains at the bases of mountains. 



