62 NEW YORK STATE MUSEUM 



Schroon Lake village. At one place many small off-shoots from 

 the dike were obse'rved to cut sharply the Whiteface anorthosite. 



A dike 6 inches wide with strike N 20° E cuts Whiteface anor- 

 thosite at the summit of Severance hill. 



A dike of very typical diabase with maxim'um width of 40 feet 

 cuts pinkish granite for one-quarter of a mile across the top of the 

 httle hill 1% miles due west of Grove Point. 



Three dikes of particular interest cut typical Marcy anorthosite 

 at the stmimit of Saywood hill. They vary in width from 6 inches 

 to i^ feet and strike N 20° W. These dikes all show rather dis- 

 tinct magmatic flow-structure foliation. Diabasic texture is absent, 

 and the fresh rock is dark gray with numerous black ferro-mag- 

 nesian minerals each from i to 3 millimeters long. A close inspec- 

 tion reveals many tiny red garnets. In thin section (no. 43 of 

 table 4) this rock is seen to be a hypersthene diabase. 



Near the top of the hill one-third of a mile due north of the 

 summit of Saywood hill there are two diabase dikes, one 15 feet 

 wide and the other 2 feet wide, traceable for a number of yards 

 in sharp contact with the Marcy anorthosite. The narrower dike 

 is probably a branch of the wider one. These dikes have a good 

 diabasic texture, and they are finer grained toward their margins. 

 Myriads of tiny red garnets are visible under the hand lens. They 

 show no foliation. A thin section (no. 44 of table 4) shows these 

 dikes to differ from those on Saywood hill by carrying 10 per cent 

 diallage, and oligoclase to labradorite instead of labradorite alone. 



On the ridge one-half of a mile north-northwest of Blue Ridge 

 village a dike 2 feet wide sharply cuts the Marcy anorthosite with 

 strike N 40° W. This dike looks almost exactly like those on 

 Saywood hill above described. 



PALEOZOIC ROCK OUTLIERS 

 Two outliers of early Paleozoic strata occur within tlie Schroon 

 Lake quadrangle. One of these, in and near the village of Schroon 

 Lake, has long been known, but the other, i^^ miles southwest of 

 the village, was located by the writer in 1916. During 1917 the 

 writer discovered another outlier in the valley of Schroon river 

 7 miles north of Schroon Lake village. The outliers at and near 

 the village are of particular geological significance, having been 

 formerly connected with the main body of early Paleozoic strata of 

 both the Champlain and Mohawk valleys, but now being isolated 

 masses from 13 to 16 miles from the Champlain valley strata. 



