38 GEOLOGY OF ERIE COUNTY 



sandstone layers. These increase in number in the Angola and 

 Hanover shales and finally culminate in the heavy bedded sands 

 of the Nunda sandstones. 



The present subdivision of the Portage beds in Erie county 

 is unsatisfactory. The Middlesex, Cashaqua and Rhinestreet are 

 constant enough in their characteristics to permit identification 

 at distant points. With the other subdivisions this is difficult. 

 Each varies at different points and each blends with the one 

 above and below it. For instance there is no line of demarcation 

 between the so-called Angola and Hanover divisions of the Hatch 

 shales. One merges into the other. Nor are they so different 

 at their most different parts to admit of positive identification. 

 Similarly the Hanover merges into the Gardeau for although 

 they are separated in theory by the black band of the Dunkirk 

 shale, this band is merely a thicker band than three others which 

 are included in the Hanover. Similarly, no line of demarcation 

 exists between the Gardeau and L,aona sandstone, nor does the 

 Wiscoy differ in character from the Gardeau. 



All the beds except the Rhinestreet increase in thickness 

 toward the east and at the same time increases in sandiness. 



Middlesex Shale. 



The Middlesex shale is a thin band of hard black shale lying 

 between the gray Cashaqua shale above and the dark West river 

 shale below. Originally this was included by Professor Hall in 

 the Genesee slates in which he also placed all the black and dark 

 gray shales lying between the Tully and the gray Cashaqua. 

 This upper member of the original Genesee slate has been 

 referred by Clarke to the Portage as its lowest member. It was 

 named from its complete exposure in Middlesex valley near the 

 head of Canandaigua lake. It disappears at Seneca lake. East 

 of Seneca lake it seems to have merged with the West river shale. 



In Erie county the Middlesex shale is a thin bed of hard, 

 black, slaty shale with a chocolate streak and a strong bituminous 

 odor. It is crossed by two series of cleavage planes along which 

 it separates into parallelograms. It splits easily into thin 

 laminae the surfaces of which after weathering are stained with 

 iron. 



