GEOLOGY OF THE SCHROON LAKE QUADRANGLE 39 



series shows many variations from quartz syenite through, granitic 

 syenite to granite. Since it is part of, and in almost every way 

 similar to, the well-known syenite-granite series of the Adirondack 

 region, it seems unnecessary to enter into detailed descriptions 

 here. The interested reader will find more or less elaborate descrip- 

 tions and discussions of the age and relations of the syenite-granite, 

 series in the various special papers and New York State Museum 

 bulletins pertaining to the Adirondack region. 



That the syenite-granite is younger than the anorthosite of the 

 quadrangle is proved by dikes and a broad tongue of granite intrur 

 sive into the anorthosite, and by inclusions of anorthosite in both, 

 the syenite and granite. Actual examples are cited above in the 

 discussion of the anorthosite. In fact, the occurrence of numerous 

 small to large inclusions and isolated areas of anorthosite in the 

 syenite-granite series as far out as 7 or 8 miles from the solid 

 body of anorthosite, strongly supports the view that the whole 

 anorthosite border was badly intruded and cut to pieces by the 

 syenite-granite magma, the present inclusions and isolated masses' 

 being merely remnants of the former more extensive body of 

 anorthosite. 



That the syenite-granite is distinctly younger than the Grenville 

 is abundantly proved by many small to large inclusions of the Gren- 

 ville, and by tongues and dikes of the syenite or granite in the 

 Grenville. Some of the inclusions large enough to be separately 

 mapped are, I mile northwest of Schroon Lake village; western 

 side of Thurman pond; one-half of a mile east of South Schroon; 

 western face of Wilson mountain; both south and west of OHver 

 pond; 1^2 miles east of Sherman pond; i% miles west-southwest, 

 and 1^2 miles north-northwest of the summit of Hayes mountain; 

 and \y 2 miles east-southeast of Boreas river. Most of these are 

 lens-shaped inclusions parallel to the foliation of the inclosing" 

 rocks. The larger masses of Grenville represented on the geologic 

 map are probably also best to be regarded as inclusions. In the 

 granite of the Lester dam mixed rock area there are numerous 

 drawn out or lenslike inclusions of hornblende gneiss. The mixed 

 rocks in the areas south of Calahan pond, southwest of Minerva, 

 west and southwest of Charley hill, north of Loch Muller, and 

 west of Schroon Lake village are Grenville gneisses all cut to 

 pieces by dikes or tongues of syenite or granite. Tongues or broad 





