106 " NEW YORK STATE MUSEUM 



from which point their thickness gradually increases towards the 

 west, and reaches its maximum in the counties of Onondaga and 

 Cayuga, where it is not less than 700 feet. The gypsum has not 

 been seen east of the western part of Oneida county. The red 

 shale comes to its end at the east end of Herkimer county; and 

 the whole group is reduced in the Helderberg in Albany county 

 to a few feet of light gray or lavender-colored, compact calcareous 

 rocks with pyrites, sepai^ating the Frankfort portion of the 

 Hudson river group from the Waterlime series.^ 



Prof. James HalP describes the iSalina group as follows : Suc- 

 ceeding the Niagara group is an immense development of shales 

 and marls with shaly limestones including veins and beds of 

 gypsum. The general color is ashy approaching drab with some 

 portions of dark bluish green. The lower part is of deep red with 

 spots of green. Succeeding this, where protected from atmos- 

 pheric influences, the rock is blue like ordinary blue clays, with 

 bands of red or brown. This portion and that succeeding it are 

 often green and spotted, and contain seams of fibrous gypsum and 

 small masses of reddish selenite and compact gypsum. From this 

 it becomes gi'adually more gray with a thin stratum of clayey 

 limestone, which is sometimes dark, though generally of the same 

 color as the surrounding mass. The formation terminates up- 

 ward with -a gray or drab limestone called by Vanuxem the "Mag- 

 nesian deposit." The red shale forming the lower division of the 

 group is well developed, but in the third district has not been 

 found west of the Genesee river. It appears in the eastern part 

 of Wayne county, as indicated by the deep red color of the soil 

 which overlies it. 



At Lockville a greenish-blue marl with bands of red has been 

 quarried from the bed of the Erie canal. West of the Genesee 

 this is the last of the visible mass. The red shale has either 

 thinned out or lost itself, gradually becoming a bluish green, while 

 otherwise the lithological character remains the same. On first 

 exposure it is compact and brittle, presenting an earthy fracture. 

 But few days are necessary to commence the work of destruction, 

 which goes on until the whole becomes a clayey mass. The pre- 

 vailing features of the second division of the group are the green 

 and ashy marl with seams of fibrous gypsum and red or trans- 

 parent selenite often embracing nodules of compact gypsum. The 

 third division comprises all the gypsum beds of the fourth district 

 which are of economic importance. In this third division hopper- 

 shaped cavities occur in Wayne and Monroe counties, but rarely 

 in Genesee or Erie. 



^N. Y. State Mus. Bui. 11. 3 :22-23. 

 ^'Geology of the 4th District. 



