GEOLOGY OF THE BLUE MOUNTAIN QUADRANGLE 9 



of this sort in the Adirondacks. One of these extends across the 

 quadrangle from the vicinity of Pine lake westward to Blue Mount- 

 ain and Utowana lakes, and the other across the northern side of 

 the quadrangle. 



Raquette river, a tributary of the St Lawrence, is the largest 

 north-flowing stream out of the Adirondack region. Blue Mount- 

 ain lake drains westward through Raquette lake into Raquette river 

 and into Long lake which latter is merely an enlargement of the 

 river itself. Two prominent northeast-flowing tributaries of the 

 upper Hudson river (Cedar river and Indian river) cross the south- 

 eastern portion of the quadrangle, Cedar river having some 15 or 16 

 miles of its course, and Indian riyer only 2 or 3 miles of its course, 

 within the map limits. Rock river, the largest feeder of Cedar 

 river within the area, has its source in the hills south of Blue 

 Mountain lake and flows eastward nearly across the quadrangle, 

 Rock lake being only an enlargement of the river. The Chain lakes, 

 which are partly within the map limits, drain southward into Rock 

 river about a mile above its mouth. In all, more than fifty ponds 

 and lakes, or parts of lakes, lie within the quadrangle. 



Excepting the glacial and postglacial deposits, all the rock forma- 

 tions of the quadrangle are of Precambrian age. Given in the regu- 

 lar geologic order they are as follows : 

 Glacial and postglacial deposits: Till, moraines, erratics, kames, 



lake deposits, etc. 

 Diabase: Two or three small dikes; nonmetamorphosed. 

 Pegmatite: Frequently found cutting nearly all types of the older 



rocks, including the gabbro ; nonmetamorphosed. 

 Gahhro: Occasionally occurring as dikes or small stocks; more or 



less gneissoid ; intrusive into the older rocks. 

 Syenite and granite: These are the most widespread rocks of the 

 region with many facies from a basic or gabbroic phase of the 

 syenite to typical granite and granite porphyry; distinctly gneis- 

 soid ; intrusive into the Grenville and anorthosite. 

 Anorthosite: Two small masses only which are separated from the 

 great area lying mostly in Essex county ; more or less gneissoid ; 

 intrusive into the Grenville. 

 Grenville series: Prominently developed only in the southern half 

 of the quadrangle ; thoroughly crystalline stratified rocks, includ- 

 ing various gneisses, limestones, and quartzite. 

 Some normal faults are present but they are far less prominent 

 than in the eastern and southeastern Adirondack region. 



