404 



KEW YORK STATE MUSEtTM 



toward the southwest^ felt the molding effect of the ice thfiist dur- 

 ing the waning stage. 



Relation to underlying rock strata 



A glance at any stratigraphic map of New York State will show 

 that the dominant drumlin area, north of the Finger lakes, lies on 

 the low ground north of the outcrop of limestones formerly called 

 Helderberg and Corniferous and over the belt of strata now known 

 as Cayugan (Salina)^ Niagaran and Oswegan (Medina), naming them 

 in descending stratigraphic order, or from south to north. These 

 strata are chiefly shales, Avith relatively thin limestones in the 

 Niagaran and some sandstone beds in the Oswegan. 



The following table gives the approximate thickness of the several 

 strata along the Cayuga meridian (corrections supplied by Mr C. A. 

 Hartnagel of the State Geological Survey). 



New York rocks along the Cayuga meridian 



Kind of rock 



Shale 



Shale 



Limestone 



Sandstone 



Lim.estone 



Limestone - 



Limestone 



Shale 



Limestone 



Shale 



Shale and limestone 



Shale and sandstone 



Sandstone 



Shale 



Shale 



The drift supply for the drumlins of any district was derived 

 mainly from the strata immediately northward. The above table 

 shows that rocks beneath the limestones which inclose the Oriskany 

 are mainly shales of great thickness. Counting the Medina 

 as one fourth sandstone and the Niagaran as half limestone we 

 have 3130 feet of shale, 200 feet of limestone and 440 feet of 



Divisions 



Thickness 

 in feet 



Erian 



■ 



1 Hamilton 

 [ Marcellus 



I 140 

 . 80 



Ulsterian 



Onondaga 



80 



Oriskanian 



Oriskany 



3 



Cayugan ■< 



'Manlius ) 

 Rondout ) 

 Cobleskill 



70 

 6 





^Salina 



I 400 





'Lockport ) 



320 



Niagaran < 



Rochester ) 





1 



^Clinton 



80 



Oswegan 



1, Medina 

 ■ Oswego 



950 

 200 



Cincinnatian ■ 



Lorraine ) 

 ^ Utica ) 



820 



