22 NEW YORK STATE MUSEUM 



in the St Lawrence and Champlain valleys, other formations 

 come in whose exact relationships have not yet been made out. 

 According to Ulrich the Pamelia is to be correlated with a part 

 of the Chazy of the Champlain valley, p^or a long time the 

 Pamelia had been described and mapped as Beekmantown lime- 

 stone, but it now seems to be pretty well established that the 

 true Beekmantown is not present along the northwestern Ad- 

 irondacks. 



The Pamelia formation (Lower Siluric) is the oldest sedi- 

 mentary mass exposed within the limits of the quadrangle. Its 

 outcropping edge, which extends from north to south across the 

 district, everywhere rests directly upon the Precambric rocks. 

 Since it outcrops at the base of the steep slope facing Black 

 river its surface exposure is small. The actual contact with the 

 Precambric may be seen in at least three places as follows: 

 Where the railroad crosses Roaring brook near Martinsburg 

 station; along the creek lyi miles northwest-north of Lyons 

 Falls ; and along the railroad ^ of a mile north of Port Leyden. 

 At a number of other places the contact is almost visible. The 

 bed in actual contact with the Precambric is always a sandy 

 conglomerate above which occur several feet of calcareous sand- 

 stones, then a few feet of bluish black, fossiliferous limestone, 

 and finally thin to thick bedded, whitish gray to bluish gray, 

 rather impure limestones which latter make up more than half 

 the section. Many of the upper, gray beds are really magnesian 

 limestones which may be burned for waterlime as has been done 

 at Lowville. The conglomerate and sandstone at the base of 

 the Pamelia represent the materials derived from the Precam- 

 bric land surface as the sea encroached upon it. According to 

 the observations of Professor Gushing on the Theresa quadrangle 

 (northward), which are corroborated by the writer on the Port 

 Leyden quadrangle, the basal conglomerate and sandstone rep- 

 resents a shifting upward horizon, due to overlap, as the sea 

 encroached upon the land from west to east. These basal beds 

 are more than likely to be correlated with the Rideau sandstone 

 as described by Ami in Ontario, Canada. 



Following is a detailed section made by Professor Cushing 

 along Roaring brook (near Martinsburg station) and kindly fur- 

 nished to the writer: 



4 inches of blue gray calcareous shale above and 9 inches of p^et Inches 

 same beneath with a 4-inch layer of mottled blue limestone 

 like that beneath i 5 



