* 



GENERAL GEOLOGICAL FACTS AND PRINCIPLES. 5 



Stage. ( C ) Chemung Series : (a) Portage Stage ; (b) Chemung 

 Stage. (Z>) Catskill Series. VIII. Carboniferous System. (A) 

 Subcarboniferous or Mississippian Series. (B) Carboniferous 

 Series. (C) Permian Series. 



MESOZOIC GROUP. IX. Triassic System. X. Jurassic System. 

 IX. and X. are not sharply divided in the United States, and we 

 often speak of Jura-Trias. A stratum of gravel and sand, along 

 the Atlantic coast, that contains Jurassic fossils has been called 

 the Potomac formation by McGee. XL Cretaceous System. Sub- 

 divisions differ in different parts of the country. Atlantic Border : 

 (a) Raritan Stage ; (b) New Jersey Greensand Stage. Gulf States : 



(a) Tuscaloosa Stage ; (b) Eutaw Stage ; (c) Rotten Limestone 

 Stage ; (d) Ripley Stage. Rocky Mountains : (a) Comanche 

 Stage ; (b) Dakota Stage ; (c) Benton Stage ; (d) Niobrara Stage ; 

 (e) Pierre Stage ; (/) Fox Hills Stage ; (g) Laramie Stage. Stages 

 (c), (d), (e), and (/) are sometimes collectively called the Colorado 

 Stage. Pacific coast : (a) Shasta Stage ; (b) Chico Stage ; (c) 

 Tejon Stage. 



CENOZOIC GROUP. XII. Tertiary System. (A) Eocene or 

 Alabama Series : Gulf States, (a) Claiborne Stage ; (b) Jackson 

 Stage ; (c) Vicksburg Stage. Western States, (a) Puerco Stage ; 



(b) Wasatch Stage ; (c) Wind River Stage ; (d) Bridger Stage ; 

 (e) Uintah Stage. (13) Miocene or Yorfctown Series, including 

 perhaps the Sumter of the Atlantic Border. On the Pacific Slope 

 it has the following : (a) White River Stige ; (b) John Day Stage ; 



(c) Loup Fork Stage. ( C) Pliocene Series. (Of doubtful Ameri- 

 can determination.) XIII. Quaternary System. (A) Glacial 

 Series. (B) Champlain Series. ( C) Terrace Series. (D) Recent 

 Series. Pleistocene is sometimes employed as a name for the early 

 Quaternary, especially south of the Glacial Drift. The Quaternary 

 granitic sands and clay of the coast below the terminal moraine have 

 been called by McGee the Appomattox and Columbia formations. 



Other terms are also often used, especially when we do not wish 

 to speak too definitely. " Formation " is a word loosely employed 

 for any of the above divisions. "Terrane" is used much in the 

 same way, but is rather more restricted to the lesser divisions. A 

 stratum is one of the larger sheet-like masses of sedimentary rock 

 of the same kind; a bed is a thinner subdivision of a stratum. 

 " Horizon " serves to indicate a particular position in the geologi- 

 cal column ; thus, speaking of the Marcellus Stage, we say that 

 shales of this horizon occur in central New York. 



