5^4 



STRUCTURE AND LIFE HISTORIES 



the following table, the older rocks being at the bottom, 

 the most recently formed at the top. 



Table VI. — Table of Geological Time 



Era 



Cenozoic 



Mesozoic 



Quaternary 



Tertiary 



Secondary 



Paleozoic 



Primary 



Archean 



Period 

 Holocene 



(recent, or the present) 

 Pleistocene 



(ice age) 



Pliocene 

 Miocene 

 Oligocene 

 Eocene 



Upper Cretaceous 

 Lower Cretaceous 

 (Comanchean) 

 Jurassic 

 Triassic 



Permian 



Upper Carboniferous 



(Pennsylvanian) 

 Lower Carboniferous 



(Mississippian) 

 Devonian 

 Silurian 

 Ordovician 

 Cambrian 



/ Huronian 

 \ Laurentian 



509. Paleogeography. — By changes in the relative 

 level of the land and sea, above referred to, rocks contain- 

 ing fossils may be elevated as dry land, and frequently 

 as mountains, so that remains of marine organisms, as 

 well as of others, are often found at high elevations. In 

 some cases forests near the seashore have been submerged, 



