GEOLOGICAL PERIODS. 



1G5 



tions,* as the group of strata of one district of distribution and belong- 

 ing to one period are named, cannot be divided petrographically or 



: The following table may serve for a bird's-eye view of the geological periods 

 anil their most important formations : 



QUARTIARY PERIOD 



/ 7T7 -7 7 177 7 



(JJiluinal and Alluvial 

 Formations) 



TERTIARY PERIOD 



(C'aiitozuic Formations). 



( alluvh . 



and fresh-water 



\ 



SECONDARY PERIOD 



(Mesozoic Formation). 



SECONDARY PERIOD 



ic formations). 







Postpllccene or Diluvial Period (erratic boulders, 



glacial period). 



f Pliocene Period (subappenine formations, bone sand 



of Eppelshcim, etc.) 

 I Miocene Period (Molasse, Tegel near Vienna, brown 



coal in North Germany, etc). 



Eocene Period J Flycb ' ^ummulitc formation 

 { of the Paris basin. 



plaestricht strata, white chalk, 

 ") upper green sand. Gault, 

 lower green sand, Weald. 



/ 



Purbeck strata, Portland stone, 

 Kimmeridge clay, Coral Rag, 

 Oxford clay, Groat oolite, 

 Lower oolite, Lias (white, 

 brown, and black jura). 



Keuper or upper new red sand- 

 stone, Muschelkalk (upper 

 Muschelkalk, gypsum and 

 anhydrite, Wellenkalk, Bun- 

 ter Sandstein). 



Cretaceous Period 



Jurassic Period 



Triassic Period 



PALEOZOIC PERIOD 



(PitLc'ozoio Formations] 



Permian \ Zcchstein, Rothliegcndes. 



lower new red sandstone. 



Coal Measures of England, 

 Carboniferous J Germany, and North 

 Period I America, Kulmformation, 



Carboniferous limestone. 



Devonian Period (Spirifereuschiefer, Cypridinen- 

 schiefer, Stryngocephalenkalk, etc. old red sand- 

 stone.) 



Silurian Period (Ludlow, Wenlock, strata, etc.) 



Cambrian Period (slate, etc.) 



( Thonschiefer, Laurentian formations. Mica schist, 

 ( Older Gneiss formations. 

 According to Professor Eam&ay the groups of formations in England have a 

 thickness of 72,584 feet, i.e., about 13| Engl'shmiles ; that is, formations of the 



Palaeozoic period have a thickness of 57,154 ~\ 

 Secondary 13,190 } 72,584 feet 



Tertiary 2,21 Oj 



ARCH.EAM PERIOD 



