NEW YORK STATE MUSEUM 



The formations involved are as follows in descending order: 



ERA OR 

 SYSTEM 



Ontario 



or 



Upper Siluric 



UNITS OF SEDIMENTATION 

 PERIOD OR AGE OR REPRESENTED IN COLOR 



GROUP STAGE ON THE MAP 



f Bertie waterlime 

 J Camillus shale 

 I Vernon shale 

 l^Pittsford shale 

 f Lockport dolomites with 

 I interbedded Giielph 

 Niagara { faunas 



I Lockport dolomites 

 1^ Rochester shale 

 f Irondequoit limestone 

 I Williamson shale 

 Clinton <( Wolcott limestone 

 Furnaceville ore 

 ^ Sodus shale 



f Upper Medina (sand- 

 Medina -( stones and shales) 



Lower Medina (shales) 



Cayugan Salina 



Niagaran { 



Oswegan 



Sequence of events preceding the deposition of the rocks of the 



Rochester area 



Although the Medina is the lowest formation that is exposed in 

 western New York, well records have shown that we have the com- 

 plete older series as known in the Mohawk valley, around the south- 

 east border of the Adirondacks and in Canada. 



The following table gives the order of succession of the rocks of 

 the Rochester region below the Ontario or Upper Siluric as deter- 

 mined from well records. 



ERA OR 

 SYSTEM 



PERIOD OR 

 GROUP 



Cincinnatian 



Champlainic or . 



Lower Siluric ' Mohawkian 



Cambric or 

 Taconic 

 Archean . . . 



Canadian 



•j Saratogan 



AGE OR 

 STAGE 



Lorraine beds ) 

 Utica shale f 



THICKNESS 

 IN FEET ' 



Beekmantown dolomite 

 (Little Falls dolomite) 



Potsdam 



598 



f Trenton limestone ^ 

 { Black River limestone y 954 

 (^ Lowville limestone J 



137 



(?) 



3 + 



1692 -f- 



I Falrchild, H. L. Roch. Acad. Sci. Proc. 1891. 1:184. There is some evidence indicating 

 the presence of the Potsdam. See 2 : 95, 102, 216, 217. 



