BUFFALO SOCIETY OF NATURAE SCIENCES 39 



It increases in thickness towards the east. Grabau gives its 

 thickness at Eighteen Mile creek as nine and a half feet though 

 Luther gives its thickness at Smoke's creek as six feet. In 

 Ontario county it is thirty-five feet thick. 



It is to be seen in the cliffs at the mouth of Pike creek. Its 

 contact with the overlying Cashaqua and the underlying West 

 river can be seen in the Eighteen Mile creek gorge just above the 

 railway bridges. An excellent exposure of the upper surfaces of 

 its layers with numerous large plant remains is found in the bed 

 of the south branch of Smoke's creek just above the Benzing 

 road. A fine exposure showing the contact with the underlying 

 West river shale can be seen in Cazenovia creek cliffs south of 

 Springbrook. 



Fossils are rare. A few layers at some points show abundant 

 plant remains. Lingula ligea is the only fossil listed from Erie 

 county. A large fish plate was found by the writer in its lowest 

 beds at Smoke's creek. 



Cashaqua Shale. 



Lying between the hard, black Middlesex shale and the 

 equally hard, black Rhinestreet is a soft, gray shale, which from 

 its excellent exposure on Cashaqua creek in the Genesee Valley, 

 was designated by James Hall the Cashaqua shale. 



It consists of an olive-gray shale which after exposure breaks 

 down readily into a gray clay. Included in the mass are rows 

 of flattened concretions which in some locations tend to coalesce 

 into thin, irregular flags. Its thickness is given by Hall as 

 thirty-three feet at Eighteen Mile creek and by Luther as 

 averaging forty-five feet in the county. It extends eastward to 

 Cayuga lake. 



The contact of the Cashaqua with the shales above it 

 and below it is fairly definite. Seen at a distance, the Cashaqua 

 when exposed in a cliff, is a well defined gray band lying between 

 two black bands, with sharply marked lines of demarcation. 

 Seen more closely the gray is found to merge gradually into the 

 black shales through a foot or more of brown or chocolate colored 

 shale. 



