the Middle Atlantic Slope. 449 



and the deposits and shore-lines alike pass beneath, and are 

 manifestly far older than, the terminal moraine. 



The predominant and most significant phenomena of the 

 formation are widespread stratified deposits and associated ter- 

 races ; and if deposits are ever proof of deposition, and if 

 shore lines ever tell of shores, the Coastal plain of the Middle 

 Atlantic slope was submerged beneath floe- bearing oceanic 

 waters during the Columbia period. 



Synopsis of Earlier Studies. — While the isolated deposits 

 representing it have not been correlated hitherto, and while 

 the chronologic and taxonomic relations of its parts were never 

 elucidated by local observers, the formation has been defined, 

 and its genesis recognized, by every geologist who has studied 

 its area. 



W. B. Rogers was one of the first to locally discriminate 

 the formation, and was also one of the last to discuss its rela- 

 tions: he recognized it in eastern Virginia in 1835,* and in 

 1839 accurately diagnosed its principal characters and inferred 

 that it was formed in an ocean subjected to strong tides and 

 currents ;f and in 1875 he described it as developed about 

 Washington, discriminated it from the newer Mesozoic (Poto- 

 mac) gravels, indicated the sources of the coarser materials, 

 noted its increasing coarseness northward, reiterated his infer- 

 ence that it represents a period of submergence sufficient to 

 fill the valleys and perhaps flood the divides of the Coastal 

 plain, and inferred further that it was formed during a period 

 of cold and floating ice probably coeval with the ice period of 

 the north 4 



H. D. Rogers recognized the formation in New Jersey in 

 1836, and inferred that the " sand and gravel" of which it 

 consists was of sub-aqueous origin ;§ and he maintained the 

 same inference in 1840. j| 



In 1841 Booth discriminated the formation in southern Del- 

 aware, enumerated its fossils, recognized its marine origin, and 

 referred it to the "after-Tertiary age.''T 



About the same time Conrad classified the later Tertiary 

 deposits of the Middle Atlantic slope,** described various ex- 

 posures of the stratified beds of the Columbia formation and 

 enumerated their marine fossils (which are all of recent and 

 local species), and referred them to the •" Pleistocene or post- 

 Pliocene." 



* Geology of the Virginias, 1884. 29-30. 



f Ibid., 253, 264, 275. 



jlbid., 709-13. 



§ Report Geol. Survey of N. J., 2d ed., 1836, 17. 



|| Description of the Geology of N. J.. 1840, 176. 



"|[ Mem. Geol. Survey Del., 1841, 94, 97. 



** Bull, of Proceedings of Nat. Inst, for Promotion of Sci., 1841, 177. et seq. 



