178 



HELDERBERG DIVISION. 



Tablc exhibiting th, thickness of the rocks composing the Helderberg division, at different placis in the 



Stat, of Mew-York. 



\ UIES OF ROCKS. 



lie 



Green shale, eypseous rock & waterlime, 



ierus limestone 



Delthyris shaly limestone 



Encrinal limestone 



Dpper Pentamerus limestone .... 



Oriskanj Sandstone 



Candm-galli eiit 



Schoharie srrit 



Onondaga and Corniferous limestone 



H 



E 

 » 

 O 



u = 

 : i 



it 



i 



§ . 



* - 



5| 



.- 



H 

 E 



a 

 o 

 6 



< 

 o 



h 



E 

 D 

 O 



o 



E 

 O 



II 



> 

 k 

 o 

 u . 



■« = 



H 

 E 

 S 



8 



a 



3 



h 

 h 



E 

 D 

 O 

 O 



M 

 M 



» 

 M 



O i 



? 



a 



■s 



E 



9 



B 





a 











o 













-j 









*• 



E 



■< 



M 



M 





o 



< 



en 



O 



S 



O 



C 



- 







w 



~ 



r«i. 



Feet 



Feat. 



5 



F<*t 



F«eL 



lert 



Fret 



FMt 



FML 



FceL 



Tea. 



500 



60 



60 



100 







100 





700* 





lOf 



700 



20 





25 







- 



4 









80 



' 



60 



60 







20 











70 



30 



10 



10 











14 







30 



3 



2 

 60 



1 



i 

 2 



i 







1, 

 10 











4 



2 



60 



4 





60 



80 







100 







75f 



50 



100 



1590 









* Vaxuxem. 







t Hall 





The Onondaga limestone, the superior rock of tin Helderberg division. The importance 

 of this rock is seen in another and different point of view, namely, in forming a distinct 

 line of demarkation between two divisions of rocks, which, though intended only as geo- 

 graphical lines in this instance at least, yet really defines the end of a series in the system. 

 Lithologically the end of the series with this rock is indicated, though it could not be 

 proved. If, however, organic bodies are permitted to speak, they tell us that such is the 

 fact ; for it is rare that those of this rock go up into the succeeding deposits, and still less 

 probable is it that any of the rocks below the Onondaga limestone reach the shales and 

 sandstones of the Erie division. This rock, then, forms or marks an era in the New- 

 York system, which must always be regarded as important; and this is true, in whatever 

 light we may regard this system : or whatever classification we may adopt, this rock must 

 form the termination of one of the divisions. It is true that the upper portions are dark 

 colored, and the layers are separated by seams of shale ; still this only proves, thai the 

 change which was about to take place was not sudden or immediate, but gradual. It is 

 probable the dark color of much of the upper part of the Corniferous limestone is of the 

 same nature as that of the Marcellus slate, the mass which reposes upon it. 



On referring to what is said in the closing remarks upon the Champlain division, it will 

 now Lv seen thai we have at least two very satisfactory divisions in the New-York system : 

 the first, ending with the gray sandstone of the Champlain division ; and the second, with 

 the Onondaga limestone. Between the lower division .mil the next succeeding, the On- 

 tario division, the affinity or resemblance is only Blight. There is, however, a greater 

 resemblance between the Helderberg division and the Erie, probably, than between the 



