GEOLOGY OF THE SCHROON LAKE QUADRANGLE II 



by subsequent erosion. The later syenite-granite magma, however, 

 had a much greater tendency to more or less intimately break up, 

 penetrate, and even engulf the Grenville strata. All except pos- 

 sibly the few largest areas of the quadrangle may well be regarded 

 as true inclusions in the syenite-granite series. 



Since nearly all the various types of Grenville rocks below men- 

 tioned in the descriptions of the Grenville areas have been described 

 in the writer's report on the Geology of the North Creek Quad- 

 rangle,'^ it seems needless to repeat the details here. 



Description of Grenville areas. The rocks of the various 

 Grenville areas are described somewhat in detail, in order to have 

 on record the more important data which may possibly aid in work- 

 ing out at least the broader stratigraphic relations of the Adiron- 

 dack Grenville series. The structural features of the Grenville 

 are discussed in the chapter on Structural Geology. Dips and 

 strikes are shown on the accompanying geologic map. 



Minerva area. This is the largest area of the quadrangle (see 

 map) and, although there are many excellent exposures, never- 

 theless they are not numerous enough to make it possible to gain 

 anything like an accurate idea of the stratigraphy and structure 

 of the area. The best exposures are north, northwest and west 

 of Minerva. South and southeast of that village there are very 

 few outcrops so that the southern boundary of the area is mostly 

 rather uncertain. Practically all the Grenville rocks of the area 

 show a northwest strike (see map). 



The little hill just west of Minerva consists of well-bedded 

 quartzitic, biotitic and hornblendic gneisses, all very typical of the 

 usual Grenville series. Just back of the hotel a small mass of 

 twisted cr}'stanine limestone lies in contact with the granite there 

 mapped. 



On the steep hillside one-half of a mile farther west the rock 

 is mostly hornblende gneiss, some with garnets, and with some 

 bands of biotite gneiss and quartzite interbedded. 



Northwest of Minerva, in and near the garnet mine, crystalline 

 limestone associated with much red garnet and green pyroxene is 

 closely involved with granite, this being separately mapped as 

 mixed rocks. Just south of the mine there is a vertical ledge, nearly 

 lOO feet high, of well-bedded granitic-looking gneiss, impure 

 quartzite, and some limestone. 



'N. Y. State Mus. Bui. 170. 



