CHAPTER IX 

 THE DEVONIAN PERIOD 



Okigin of Name, Subdivisions, etc. 



In 1839 Sedgwick and Murchison gave the name of Devonian to 

 strata in the county of Devonshire in England where rocks of this 

 age were first carefully studied. Because of the metamorphosed 

 and highly disturbed character of the English Devonian, the 

 sub-divisions in Europe were not well worked out until the more 

 undisturbed rocks of Belgium and along the Rhine were studied. 



In North America the New York subdivisions are taken as the 

 standard, because the Devonian strata were first carefully studied 

 there. The New York Devonian section is a remarkably complete 

 one of very considerable thickness (fully 4000 feet), with not a 

 single stage missing, except possibly the very lowest one, and with 

 a surface distribution over fully one-third of the area of the state. 

 There was well nigh continuous deposition of strata during Devo- 

 nian time in New York, and if locally a stage or sub-stage is missing, 

 it is present elsewhere in the state. It is doubtful if a greater 

 degree of refinement of knowledge exists, regarding so complete a 

 section of the Devonian or any other Paleozoic system in North 

 America, than that of New York state. 



The latest classification of the New York Devonian system by 

 the State Geological Survey follows: 



Chautauquan I chemung and Ca tskiU sandstones. 



Upper Devonian - 



series 



Senecan 

 series 



f Portage sandstones and shales. 

 I Genesee shales. 

 ( Tully limestone. 



Middle Devonian 



f Erian 

 series 



Ulsterian 

 series 



Hamilton shales and limestone. 

 Marcellus shales and limestone. 



Onondaga limestone. 

 Schoharie grit. 

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