96 NEW YORK STATE MUSEUM 



sented by a belt that stretches east and west from the town of Knox, 

 Albany county, to the Niagara river at the western border whence 

 it continues into the province of Ontario, Canada. The belt is 

 thus about 250 miles long; in width it varies all the way from less 

 than a mile to 20 miles wide. The maximum width, as well as 

 thickness of the strata, is attained in central New York in Onondaga 

 and Cayuga counties. The strata have a low dip (averaging about 

 50 feet to the mile) to the south, which carries them under the 

 higher members of the Silurian and of the Devonian rocks that 

 spread over the area lying between the Salina and the Pennsylvania 

 state line. 



The Salina strata consist of shales, limestone, rock salt, anhydrite 

 and gypsum. The uppermost layers are usually argillaceous lime- 

 stone, to which the name Bertie waterlime is given. The rock 

 forms a capping for a large body of shale, with intercalations of 

 limestone bands, known as the Camilltis shale, usually drab in 

 color. It is in this formation, and commonly within 100 feet or 

 so of the top that the gypstmi beds occur. The total thickness of 

 the shale and gypsimi probably reaches 300 feet in central New 

 York. Below the Camillus lies the rock salt which has been traced 

 from Madison county west to Erie county, and the red Vernon 

 shales which are the thickest member of the Salina, attaining about 

 500 feet in the vicinity of Syracuse. The horizon of the salt can 

 not be determined accurately with reference to the gypsum, since 

 the beds do not extend to the outcrop and few of the drill records 

 in the salt district make any mention of gypstim or the related 

 mineral anhydrite. It appears probable, however, that the interval 

 is a variable one and may range from 50 to ■ 200 feet or more in 

 different places. 



The Camillus formation in western New York holds an important 

 calcareous element, particularly in the upper 100 feet which is largely 

 composed of thin-bedded magnesian limestones, scarcely different 

 in appearance from the Bertie layers above. The gypsum is asso- 

 ciated with these limestones in seams arranged parallel with the 

 bedding. A foot or two of gypseous shale, so-called " ashes," usually 

 accompanies the deposits, most commonly lying above in imme- 

 diate contact with the gypsiim. It weathers rapidly and conse- 

 quently makes a poor roof. It looks more like a residual product 

 of the limestone beds than a true shale and seems to diminish or 

 disappear in the deeper zone. A section of the gypsum beds, showing 

 the characteristic order, is here given from the Akron district. 



