NEW YORK STATE MUSEUM 



The old group terms commonly employed in combining the units repre- 

 sented in the above table have now entirely lost their value and hence do 

 not appear here. In this and a previous paper the precise value of the 

 geologic term Chemung is demonstrated and it now becomes a unit term in 

 accordance with its original usage. Hence there is no place in the nomen- 

 clature for the expression Chemung group, and its use involves an objection- 

 able duplication of terms. On previous occasions also it has been shown 

 that the High Point sandstones of the area next west are continuous with the 

 original Portage sandstones of the Genesee valley; hence we can not wisely 

 employ the term Portage group. Likewise the Genesee shales have been 

 restricted to the lower measures of the group passing under this name and in 

 accordance with the original intention the term becomes a unit name. Study 

 of the typical sections of the Hamilton shale in Madison county makes it 

 equally clear that the name Hamilton will not be advisedly employed except 

 as a unit and not as a group term. 



Under the former grouping, the units here embraced under the term 

 Senecan would te divided as follows from above down. 



f High Point sandstones ) . • ^, , . 



| West Hill flags ' contain Chemung fossils in Ontario 



| Grimes sandstone \ county 



t) . J Hatch shale 



mortage , Rhinestreet shale 



| Cashaqua shale 

 j Middlesex shale 

 L Standish shale 

 i West River shale 

 Genesee -j Genundewa limestone 

 ( Genesee shale 

 Tully Tully limestone 



MESODEVONIC 



Moscow shale 



The lowest formation exposed within the limits of these quad- 

 rangles is the Moscow shale, of which there are a few small out- 

 crops of its upper beds along the Keuka lake outlet between the 

 Seneca paper mills and the east line of the quadrangle, half a mile 

 below. 



In Bruce's gully, a mile farther east, 40 to 50 feet of the upper 

 part, capped by the Tully limestone, at the top of the falls, are 

 finely exposed in the sides and bottom of the ravine. 



A vertical section of this entire formation is well shown in the 

 gorge of Kershong creek at Bellona near the northeast corner of 

 this quadrangle. 



It is composed of a mass of mostly soft, light bluish, gray cal- 

 careous shales becoming darker toward the upper part. Thin 

 layers of limestone usually extending but a few rods and irregular 

 calcareous lenses, consisting principally of fossils, are of frequent 

 occurrence. 



Normally the Moscow shale rests upon a stratum of limestone 

 formerly called the Encrinal limestone but now known as the Tichenor 

 limestone from its favorable exposure at and near Tichenor point, 

 Canandaigua lake. In Ontario county the shale formation has a 



