l8 NEW YORK STATE MUSEUM 



The shale is shown at numerous localities about Rochester and 

 ii excavating in the north part of the city the shale is often 

 encountered. It may also be observed near the canal in the 

 town of Greece and in several of the ravines leading to Irondequoit 

 bay. 



The Rochester shale is known as far eastward as Oneida county, 

 and i^robably extends still farther east into Herkimer county where 

 a shale similar to it is found just below the concretionary layers of_ 

 the Lockport dolomite. It is well developed at Wolcott in Wayne 

 county where it is seen at the falls in the village. From here to the 

 Niagara river, it outcrops at many points. At Niagara it forms the 

 lower 80 feet of the falls escarpment. The Rochester formation has 

 a wide distribution in the interior of the United States where, 

 though the lithologic features have changed, it may be recognized 

 by the fossils. 



In the Rochester region this shale is about 85 feet thick. It is of 

 quite a uniform dark blue color at the ba5.e and nearer the "top it 

 becomes lighter in color, where the bands of limestone appear. The 

 shale as a whole is very evenly bedded and the layers vary but little 

 in hardness and as a result the faces of some of the shale cliffs are 

 very even. On exposure it changes to a lighter color. The upper 

 layers are hard and quite resistant and have been quarried for 

 foundation purposes. The lower part when freshly excavated 

 appears quite firm, but on exposure it checks rapidly and soon dis- 

 integrates into clay. 



The Rochester shale is very rich in fossil remains. .At the 

 base, fossils are not numerous, but a few feet above they become 

 abundant. Toward the top they again become less abundant, the 

 upper few feet being practically barren. Fossils may be obtained 

 along the gorge where is found much talus material. This is 

 often badly broken up, but fragments of the harder calcareous layers 

 are found with fossils in abundance. Excavations in the soft shales 

 often bring to view fine specimens, but if not immediately collected, 

 they will be destroyed through the disintegration of the mass which 

 quickly follows. The excavations for the new barge canal in the 

 town of Greece are at present in the Rochester shale and undoubtedly 

 large collections could be made at this point. The number of 

 species recorded is very large and the following list includes the 

 more common forms found in the Rochester region: 



