CENOZOIC TIME — TERTIARY. 933 



of India, the beds above the Nummulitic formation at the top of the 

 upturned series are probably Miocene, as indicated by the plant beds, one 

 species, the Sahal major, ranging from Lower to Middle Miocene in Europe. 

 The Siwalik Tertiary beds (of the Sub-Himalayas), many thousand feet 

 thick, along the length of the Himalayas, which are Pliocene with probably 

 Upper Miocene at top, rest on the inferior Mesozoic and Paleozoic rocks 

 along what appears to be an enormous fault-plane. This steep "fault- 

 plane," as shown by Medlicott, is really an original limit of deposition, in 

 part almost cliff-like, to the north of which the Siwalik beds never extended. 

 These beds are, therefore, not included in the disturbed region. There 

 appears to be doubt remaining whether the epoch of upturning followed the 

 close of the Nummvditic Eocene or that of the Miocene. 



The mountain chains to the north of the Himalayas for 22° of latitude 

 are nearly parallel to it, and this has led to the suggestion that all this great 

 region in Asia was involved in one system of orogenic movements. 



Epeirogenic movements chiring the Tertiary era. — Through the Tertiary, 

 changes of level went slowly forward by geanticlinal bandings of the earth's 

 crust and slippings along old or new fracture planes, giving great altitude to 

 vast continental areas, and especially those within 800 miles of the sea- 

 border, and affecting all the continents alike with the same stupendous results. 

 The continuing of the movements through all Tertiary time, and also beyond 

 it, during part of the Quaternary, teaches that they were extremely slow in 

 general progress ; yet sudden slips of scores and hundreds of feet were 

 probably among the events. 



In the Rocky Mountain region the change was slight during the Eocene, 

 and yet it was sufficient to modify the outlines and positions of the Eocene 

 lakes. With the close of this period, the land was so far raised that the 

 Eocene lakes were drained; but the elevation attained was so small, as 

 Hayden first remarked, that vast Miocene lakes covered a large part of what 

 now constitutes the eastern slopes of the mountains, and continued into the 

 Pliocene. The long continuance of the lakes indicates not only slowness of 

 emergence, but also that the movements were interrupted through long 

 intervals. The western margin of the Nebraska lacustrine beds is 3500 feet 

 above the level of the eastern, the former having a height of about 6000 feet 

 and the latter of 2000 feet. This is proof that the elevation of the moun- 

 tains went on through the Pliocene, for the rise to the westward could not 

 have made much progress in the Miocene without drying up the lake. 



The height which the Rocky Mountains had reached by this change of 

 level is not ascertained. This much is known : (1) that the Cretaceous areas 

 were originally at or near the sea level ; and (2) that within the area of the 

 United States the present height of the upper beds is now, in part, 13,000 

 feet. Moreover, the corresponding height in central Mexico is 10,000 feet, 

 and in British America, toward the Arctic seas, 4000 feet. 



During the progress of these changes over western North America there 

 were also, according to Gilbert, Powell, LeConte, and others, faults along 



