REPORT OF THE DIRECTOR I904 



13 



distance of 10 miles. The boundary has been carefully followed 

 and plotted. Both of these masses become more obscure and 

 gneissoid near their edges, and the usually weathered phases of 

 the resulting rocks are closely alike and difficult to distinguish 

 in the field. Considerable masses of syenite are found within 

 the anorthosite area, and the reverse is also true. It is not pos- 

 sible that both were extruded at the same time but decisive evi- 

 dence has not been acquired, although in all probability the 

 syenite is the younger. The syenite is frequently cut by a 

 younger granite, small dikes of which are also found occasionally 

 in the anorthosite. 



The southern half of the quadrangle is occupied by gneisses 

 with an extensive development of the peculiar schists and 

 gneisses which are old sediments of Grenville age. Crystalline 

 limestones occur with these in some measure. The extensive 

 development of the Grenville series in this area was unexpected, 

 and it will be necessary to revise our previous views as to the 

 extent of these rocks in the immediate region of the^mountains. 

 The gneisses are mainly red and biotitic, probably of the com- 

 position of granites though showing a considerable variation. 

 With these are amphibolites which locally pass into hyperite 

 gabbros of which the amphibolites, in part at least, are a meta- 

 morphosed phase. In the southwest the gneisses differ some- 

 what and are to some extent involved with the granite. The 

 granites are also found cutting the Grenville rocks. These 

 gneisses are free from admixture with characteristic Grenville 

 rocks and seem to represent a whole distinct rock series, though 

 no exposures were found which gave any clue to the relations of 

 the two. A single large diabase dike was located on Camp island 

 in Long lake. 



In the north half of the sheet the region of the high Adiron- 

 dacks is touched on the east ; midway is the low ground of the 

 lake belt, here rather poorly defined, west of which are higher 

 syenite peaks. On the south the gneisses furnish more rounded 

 hills than do the eruptives and the Grenville rocks are mainly 

 found in the valley levels. 



Stratigraphic geology 



Areal maps. The work of producing stratigraphic maps on 

 the topographic base has progressed in several parts of the State. 



In these maps we have endeavored to make the stratigraphic 



