From Eocene to Recent Time 241 



Apennines, Alps, Carpathians, Himalayas, and minor 

 mountain ranges between, were as yet incompletely elevated 

 or were still submerged areas. 



But from late Eocene to early Oligocene time diastrophic 

 activity caused increasingly enormous elevation of this area 

 in some centres, and corresponding depression in others to 

 form the Mediterranean, Red Sea, or Persian Gulf. These 

 changes gave rise to great faults, and caused pronounced 

 volcanic activity, largely probably from frictional heating 

 and melting of subterranean or submarine strata, over the 

 areas affected. Such culminated in at least four important 

 results: (i) The above-named mountain-masses became 

 elevated high above sea-level as huge ridges of land from 

 8,000 feet to 16,000 feet at least high, over the sides, or 

 even as in the Alps over the tops, of which the nummulitic 

 beds were upraised. (2) Extensive outflows in part of 

 subaerial, in part of submarine volcanic tuffs, diabases, and 

 related rocks took place from Italy eastward to Tasmania, 

 also over at least Western America. This must have caused 

 sudden and widespread death of both marine and fresh 

 water fishes, as well as great deposits of volcanic dust beds, 

 such as Russell has traced. (3) The nummulitic organisms 

 suffered so severely that they soon dwindled in importance, 

 and largely disappeared toward the close of the Oligocene. 

 (4) Many species and even genera of fishes suffered ex- 

 tinction, and when heaped in masses over many hundreds 

 of miles, gave rise in time to those rich accumulations of 

 petroleum shales and sandstones, whose existence and 

 wealth are only now being made known in all their fullness. 

 As compared with statistics already given for Cretace- 

 ous and early Eocene days, it might be added that of known 

 Eocene genera still living there are 60, of which nearly 

 all of the most primitive are and have been freshwater, or 

 have only in part passed into the sea. Of these latter there 

 are 25. The remaining 35 genera include freshwater forms 

 and a greater or less number of more specialized marine 

 types in nearly every case. Not a few of them frequent 

 the coast lines at the present day; only the larger, more 

 powerful, or most highly modified genera like the tunny, 

 cod, conger eels, etc., being oceanic or deep-sea. 



