GEOLOGY OF THE PORT LeYDEN QUADRANGLE ^7 



A section measured by the writer ly^ miles north-northwest of 

 Lyons Falls, and along Mill creek, shows about 54 feet of Lowville. 

 This section is continuous with that of the Pamelia already referred 

 to. Near Denley the section contains about 57 feet of the Lowville. 



A comparison of the sections at these widely separated localities 

 brings out some interesting facts, the chief one probaibly being that 

 the formation shows almost exactly the same thickness throughout 

 the whole distance. This is especially significant in view of the 

 rapid thinning of the underlying Pamelia. Another fact is the 

 great similarity of the beds in the different sections. Thus the basal 

 conglomerate always lies from 54 to 57 feet below the summit, 

 while another conglomerate apparently always lies about 26 or 28 

 feet below the summit and is associated with a heavy bed of pure 

 dove limestone full of gastropods. 



Near the west edge of the Remsen quadrangle, along Black river, 

 there is no complete section, but the Lowville is probably not over 

 40 feet thick. On the Little Falls sheet the Lowville varies in 

 thickness from 5 to 21 feet, while at Canajoharie it is absent 

 altogether. Thus the outcropping Lowville along the southwestern 

 Adirondacks shows a steady increase in thickness in passing^ from 

 Canajoharie to Port Leyden. 



Black River limestone 



The Black River limestone is so named because of its typical 

 occurrence along Black river. It is a hard, fine grained, dark 

 colored to almost black, limestone which breaks with a smooth frac- 

 ture. Interspersed through the limestone, in a very irregular man- 

 ner, are small patches of black shale which causes the rock, on 

 weathering, to break into lumpy masses. The appearance of the 

 rock is pretty well shown in plate 6. After long exposure to the 

 weather the surface color changes to a light gray. The rock i:, 

 generally massive although two or three layers can usually be fairly 

 well made out. Another distinctive feature of the rock, particularly 

 the upper portion, is the presence in it of many irregular shaped 

 black chert nodules. Among the abundant fossils are fine large 

 specimens of orthoceratites and columnar corals especially well 

 exhibited on the upper waterworn surfaces. Hall ^ says of the 

 formation " from being characterized by a large number of peculiar 

 fossils, though mainly belonging to a single family, it is regarded 

 as worthy of separate notice. The principal and most prominent 



' Palaeontology of N. Y. 1847. i :46. 



