222 



Report of the State Geologist. 



fossils are abundant at this horizon. This limestone band is of considerable 

 value as a bench mark, as it is exposed in many places and is easily recog- 

 nized. The most easterly exposure is at Foster's gully in Middlesex, Yates 

 county. It is seen in the Seneca gully and elsewhere along the shores of 

 Canandaigua lake, and in Mill gully, in the town of Richmond, Ontario 

 county. It forms the crest of the falls in Fall brook, Geneseo, and in the 

 ravine near Moscow. The dam across the Genesee river at Mt. Morris is built 

 upon it. It is exposed in a small ravine two miles north of Wyoming, and at 

 Griswold, Darien, on Cayuga creek, Erie county, at Iron Bridge mills, and at 

 numerous other localities. It is three to five feet thick in Ontario and Liv- 

 ingston counties, diminishing toward the west to a single layer eight inches 

 thick on the shore of lake Erie, its position in the middle of the Genesee 

 slate being maintained the whole distance. 



The Styliola band divides the Genesee slate into two parts of about 

 equal thickness. The lower part is composed principally of densely black 

 slaty shale, with a conspicuously jointed structure, the joints being one and 

 one-half to two and one-half feet apart and crossing each other so as to form 

 rectangular or diamond shaped blocks. Above the Styliola band the shales 

 are mostly blue black and less slaty. Thin layers of the more bituminous 

 variety are interstratified at intervals of four to six feet and a thicker stratum 

 of the same is found at the bottom of the beds next to the Styliola limestone 

 and another at the top of the formation. Spherical concretions of all sizes up 

 to three feet in diameter, in rows or isolated, are found in large numbers in 

 these beds. 



In Ontario and Yates counties there are a few feet of olive shales and 

 bluish flags just beneath the upper black bed, that have the character of 

 transition shales between the Genesee and Portage rocks. 



The black bed thirty to forty feet thick at the head of Canandaigua lake 

 has sometimes been called the Lower Black Band of the Portage Group. 



The " transition " beds thin out toward the west, and all of the black 

 shales up to the base of the Cashaqua shales are usually considered as 

 belonging to the Genesee shales. The total thickness of the formation is 135 

 feet in the Genesee valley, 100 feet in the Oatka valley, and but twenty-four 

 feet at North Evans on lake Erie. 



The wells of the Royal Salt Company, at Mt. Morris, and of the Lacka- 

 wanna Salt Company, two miles west of Mt. Morris and the Moulton well 

 at Pearl Creek are the only salt wells that have the Genesee as the surface 

 rock. 



