TERTIARY SYSTEM. 85 



Jthe south adjoining the Gulf Coast. Fossil shells of species now living on the 

 adjacent coast, abound at every point, and demonstrate beyond reasonable doubt the 

 climate and the waters on the eastern and southern coast of the United States, and 

 in California, were then the same that now prevails. There is no pal aeon tological 

 evidence, so far known, that the Pliocene climate was different from the present on 

 this continent, and as the outlines of the continent were then nearly as they are 

 now, no material difference can be inferred. The Pliocene graduates into the 

 Post-pliocene, so that separation of the strata frequently becomes impracticable, and 

 an arbitrary approximating line for separation is assumed. The Pliocene lake 

 deposits in Nebraska, are called the Loup Fork Group, and have a thickness of 

 400 feet and cover a great extent of territory, and in North-western Kansas have a 

 thickness of 500 feet. In Wyoming they have a thickness of 1,500 feet, and are 

 called* the Niobrara Pliocene. In Bear River Valley they are called the Salt Lake 

 Group and the Cache Valley Group, and the thickness is from 500 to 1,500 feet. 



§ 189. The Post-pliocene is represented by marine deposits on the coast, and 

 by drift, sand, and gravel, in the middle part of the continent. In South Carolina 

 it is confined to a belt along the coast 8 or 9 miles wide, and the fossil shells are 

 those of species inhabiting the coast. In Los Angeles Valley, in California, the 

 thickness is 500 feet; but where depressions upon the coast have been filled the 

 thickness may be 1,000 or 1,500 feet, and so at the mouths of rivers whsre a delta has 

 been formed, as at the mouth of the Mississippi, the Post-pliocene becomes of very great 

 thickness. There are some Lake deposits of this age in the great West, which 

 have a thickness of 500 feet or more. The marine Post-pliocene is usually conform- 

 able with the Pliocene, and graduates into the present deposits without disturbance. 

 In South Carolina the bones of horses, hogs, dogs, rabbits, beavers, tapirs, and 

 other mammals occur in the layers of blue mud and sand throughout the period. 

 At some time during this age, man made his appearance on this continent, for none 

 of his work is found preceding it, nor preceding the drift ; but his stone implements 

 are associated with the remains of the mastodon and mammoth, and such animals as 

 survived the drift period in such condition as to show they lived at the same time. 



§ 190. During the Post-pliocene era, a portion of the country about Hudson's 

 Bay was submerged by the ocean, a3 shown by the fossiliferous marine sands and 

 clays occurring at 300 or 400 feet above the present level of the ocean. The rocks, 

 too, are striated in all directions, as if done by icebergs or shore-ice holding angular 

 fragments of rock. The New England States and New Brunswick, and that portion 

 of Canada south of the St. Lawrence River and east of the vicinity of Montreal, 

 was submerged, with the exception of the mountain elevations. Several beaches 

 are shown at Murray Bay 90 miles below Quebec, varying from 30 to 326 feet 

 above the bay; like beaches occur at Montreal and at various other places in this 

 part of Canada. All these deposits abound in marine fossils belonging to living 

 species in the Gulf of St. Lawrence and on the near coast of the Atlantic. The 

 surface of the rocks below these deposits is polished and striated in the direction of 

 the St. Lawrence Valley. Like phenomena occur over New Brunswick and the 

 New England States, and extending as far south as the mouth of the Hudson ; but 

 they appear on no other part of the continent. These deposits contain no terrestrial 

 or fresh'- water fauna, and, so far as the marine life is concerned, connect the lowest 

 of the clays with the present time by an unbroken chain of animal existence. 



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