BUFFALO SOCIETY OF NATURAL SCIENCES 37 



The West river shale in Erie county is composed of dark 

 gray or chocolate colored shales interbedded with thin layers of 

 hard dark shale. It merges gradually downward into the 

 Genundewa, the junction being a thin band of shale in thin 

 laminae alternating with thin limestone layers. It is fissile, and 

 splits readily into thin, sharp laminae with sharp edges. It 

 weathers rather quickly in a cliff into a rough, ragged face with 

 innumerable sharp edges projecting from it. 



The West river thickens toward the east. Grabau gives its 

 thickness at Eighteen Mile creek as eight and a half feet. At 

 Smoke's creek it is fourteen feet, and at Cazenovia creek slightly 

 more. At Mount Morris it is sixty-five feet and at Naples ninety 

 feet thick. 



The West river shale is exposed in the L,ake Erie cliffs at the 

 mouth of Pike creek. It appears in the bed of Eighteen Mile 

 creek just above the railway bridges and rises in the cliffs until 

 it disappears at their top just above the bridge over the L,ake 

 Road. A good section is exposed in the south branch of 

 Smoke's creek at the Benzing road. Its best exposure in Erie 

 county is in the cliffs of Cazenovia creek at Springbrook, where 

 its contact with the Middlesex above it and the Genundewa below 

 is well defined. 



Fossils are rare in the shaly layers but less rare in the 

 limestone layers at the bottom. Pterochaenia fragilis is the only 

 fossil listed as being found in the West river of Erie county. 



The Portage Beds. 



The Portage beds comprise that portion of the rock formation 

 ascribed by Hall to the Devonic system lying between the Genesee 

 beds below and the Chemung beds above. They approximate 

 twelve hundred feet in thickness and stretch completely across 

 the state. They extend southwesterly across the northwest 

 corner of Pennsylvania and correlate with the Ohio shales of 

 Ohio. 



In general they comprise alternating masses of black and 

 gray shales which increase steadily upward in sand content. 

 They begin with the Middlesex shale, a black shale without 

 sand. In the Rhinestreet, also a black shale, are occasional 



