370 W. Upham — Marine Shells and Fragments 



To such glacial thrust and uplifting I would attribute likewise 

 the tilted condition of the beds forming the base of Sankoty 

 Head and the elevation of the included layers of shells. More 

 than this, I believe that the same cause will account for the 

 elevation and folding of the wonderful section of steeply in- 

 clined Miocene strata which underlie the terminal moraine in 

 Gay Head.* It may well be true, therefore, so far as paleonto- 

 logic evidence can inform us, that this part of our coast, ex- 

 tending south to the farthest limit reached by the continental 

 ice-sheet, held approximately the same relation to the sea level 

 in preglacial and interglacial time as now.f During the final 

 melting of the ice-sheet, however, the land was higher, or, as I 

 would prefer to say, the sea was lower than now, as is shown 

 by channels of drainage, which extend southward from the 

 terminal moraines across the bordering plains of modified drift 

 of Long Island, Martha's Vineyard, Nantucket, and Cape Cod, 

 continuing beneath our present sea level.:}: Nor have we any 

 proof in marine beds overlying the glacial drift that the sea 

 there has stood higher than now at any time since the glacial 

 period. 



Near Boston and northeast to Cape Ann the coast seems to 

 have been submerged to a slight depth, probably not exceed- 

 ing 10 to 25 feet, when the ice-sheet retreated from this area.§ 

 In New Hampshire this submergence amounted to 75 feet or 

 more, and the fossils in the marine beds overlying the glacial 

 drift, being partly of arctic and partly of temperate range, 

 show that the severe climate of the glacial period was gradually 

 changed until the ocean became as warm as now before it 

 sank to its present level. || After this the ocean within recent 

 times has held even a somewhat lower level than at present, 

 and seems to be now very slowly rising upon this shore and in- 

 deed along the entire coast from New Jersey to the Gulf of 

 St. Lawrence, as is shown by submerged stumps of trees in 



* Hitchcock's Geology of Massachusetts, 1841 ; Lyell's Travels in North Amer- 

 ica in 1841-2, vol. i, pp." 203-6. 



f The fossils in South Marshfield and Duxbury, Mass., which I once referred to 

 the Pleistocene (Am. Naturalist, vol. xiii, p 557), extend back to the Miocene in 

 the Southern States, and seem more probably to be of similar age with the beds 

 of Gay Head (Hitchcock's Geology of Mass., 1833, pp. 199-201; do, 1841, pp. 

 91, 427). 



\ This Journal, III, vol. xiii, 1877, pp. 142-146, and 215; vol. xviii, 1879, pp. 

 89, and 198-205. Am. Naturalist, vol. xiii, 1879, p. 553. 



§ Evidenced by layers of shells of the common or long clam, mussel, oyster, 

 and other species at Lechmere Point in Cambridge (Outlines of the Mineralogy 

 and Geology of Boston, before cited, p. 96), and by fossils discovered by Profes- 

 sor Shaler at Gloucester, Mass. (Proceedings B. S. N. H., vol. xi, 1868, pp. 

 27-30). In the same notice with the former of these localities, the authors men- 

 tion a stratum of clam shells, observed on the side of a hill in Cambridge at the 

 distance of a half mile from the Charles river, which seems from its description 

 to be probably an aboriginal kitchen-midden. 



[| Geology of New Hampshire, vol. iii, pp. 165-7. 



