ROCHESTER AND ONTARIO BEACH QUADRANGLES 13 



The Clinton in this section is made up of a rather complex series of 

 limestones, shales, sandstones, and beds of iron ore. On account of 

 the variable nature of this formation, it was termed by Vanuxem 

 the " Protean group." The maximum thickness is in the vicinity of 

 Clinton and from this point the formation thins both to the east and 

 the west. In Wayne and Monroe counties, five distinct divisions 

 can be recognized. The section of the Clinton rocks as exposed in 

 the Genesee gorge is complete, every foot of the formation being 

 accessible. On account of the fine sections shown at Rochester and 

 farther east in Wayne county, it has been deemed advisable to 

 describe the different units of sedimentation under distinct names. 

 This it is hoped will in the future be an aid in the attempt to work 

 out the relation between the Clinton of central and western New York. 



The names of the subdivisions of the Clinton beginning with 

 the lowest are as follows: (i) Sodus shale; (2) Furnaceville iron 

 ore; (3) Wolcott limestone; (4) Williamson 3hale; (5) Irondequoit 

 limestone. 



Sodus shale. This is a bright green shale and at Rochester it is 24 

 feet thick. The name is from the town of Sodus in Wayne county 

 where this division is well shown in the vicinity of Sodus bay. This 

 shale succeeds the Medina abruptly. It appears to be much thinner 

 at some points in Wayne county than at Rochester, but thins in 

 going west, and at Niagara it is but 6 feet thick. The shale is quite 

 soft, splits into very thin layers and is easily broken up, and 

 when exposed to the atmosphere changes into a greenish, claylike 

 material. The shale of the lower division is very unctuous and may 

 be distinguished from the upper shale by its more uniform color, the 

 absence of limestone bands and by the almost complete absence of 

 fossils. The few fossils that do occur are mostly so called fucoids 

 which remain attached to the lower side of the firmer bands of rock 

 when the latter are removed. A number of imperfectly preserved 

 brachiopods are also found. 



The best exposure of this rock is in the gorge between the lower 

 and middle falls of the Genesee. It is well shown for a considerable 

 distance along the gorge where it is seen to rest upon the " gray band " 

 of the Medina. Another readily accessible exposure is along Dens- 

 more creek 1 at which place fucoids may be obtained. 



1 It is probable that sewer excavations now in progress along Densmore creek, will destroy 

 the section which at present is favorable for the study of the lower Clinton. 



