320 I. Bowman — Atlantic Preglacial Deposits. 



not implied that such conditions may not have occurred else 

 where, but that such was not the case here is clearly proved. 

 The presence of the yellow sands was noted by Upham and 

 also the lignitic clays, " laminated dark gray clay," the latter 

 being attributed to deposition of material subglacially trans- 

 ported, the lignites being explained as the possible remnants of 

 an interglacial forest overwhelmed by the ice, yet the absence 

 of all bowlders and till fragments in the clays was observed. 

 The better section of today shows also that the structure of 

 the till is in reality like that shown in fig. 3, and not obscurely 

 laminated. The same figure'shows the presence of seams and 

 lenses of gravel within the till, their absence having been 

 asserted heretofore. The various anomalies, which Upham's 

 observations led him to believe were present here, were 

 explained by the suggestion that the modified drift of Third 

 Cliff was deposited under very unusual sub-glacial conditions. 



Occurrence of Preglacial Deposits near Third Cliff. 



Deposits of pre-Pleistocene age once subaerially eroded and 

 now submerged have been presumed by several writers to 

 occur near shore on the floor of the sea north of Martha's 

 Yineyard. The first to suggest this, with the possible excep- 

 tion of Hitchcock, who vaguely refers to this matter (p. 427), 

 was Verrill,* who observed in dredged material from the 

 north Atlantic coast compact calcareous sandstone and arenace- 

 ous limestone bearing fossil shells and fragments of lignite. 

 About half the fossil forms were considered extinct. Ver- 

 rill thinks that the fragments were probably " detached from 

 a very extensive submerged Tertiary formation at least several 

 hundred miles in length, extending along the outer banks, 

 from off Newfoundland nearly to Cape Cod and perhaps 

 constituting, in large part, the solid foundations of these 

 remarkable submarine elevations." 



Later on, Uphamf reports finding fossils of possible Eocene 

 or Cretaceous age in the drift materials near Highland Light, 

 Cape Cod. Hitchcock:); even believed from the Miocene 

 deposits at Marshfield (seven miles south of Third Cliff) that 

 deposits of Tertiary age occurred " abundantly along the coast 

 from Marshfield to Plymouth and not improbably also on Cape 

 Cod," although their actual occurrence was not noted. 



Professor Shaler, in his report on the geology of the Cape 



Cod District,§ suggested the presence, at least on the sea floor, 



• * " Occurrence of Fossilif erous Tertiary Kocks on the Grand Bank and 

 George's Bank.' r This Journal (3), xvi, pp. 323-324, 1878. 



\ Marine shells and fragments of shells in the till near Boston, B. S. N. H. 

 Proc, xxiv, pp. 127-141, 1889. 



\ See footnote, p. 9. 



§"The Geology of the Cape Cod District," by N. S. Shaler, 18th Annual 

 Eeport, U. S. G. S. Part II, p. 580, 1896-97 (see also pp. 516 and 578). 



