8 NEW YORK STATE MUSEUM 



Lakes are notably less conspicuously developed than usual in the 

 Adirondacks, there being none of large size. Best known is Lake 

 Luzerne at the village of Luzerne (see plate 4). It is about three- 

 fourths of a mile long and of very irregular shape. It lies 624 feet 

 above sea level. An interesting chain of three small lakes — Efner, 

 Jenny and Hunt — lies in the southwestern part of the quadrangle 

 at an altitude of about 1170 feet. They range in length from one- 

 half to three-fourths of a mile. A chain of three considerabl)' 

 smaller lakes (or rather ponds) lies just east of the state road a 

 few miles north of Luzerne. Wolf pond, 1650 feet above the sea, 

 has a picturesque setting in a small flat-bottomed valley nearly 

 wholly surrounded by mountains. A number of other ponds need 

 not be specially referred to. 



Geologically, the Luzerne quadrangle shows representatives of 

 nearly all the important types of Adirondack Precambrian rocks 

 except the anorthosite, which latter is almost wholly confined to 

 Essex and Franklin counties. Oldest of all is the Grenville series 

 representing exceedingly ancient (Archeozoic) strata, originally 

 sandstones, shales and limestones, which have been thoroughly 

 metamorphosed, mainly by crystallization under conditions of heat, 

 pressure and moisture, into quartzites, schists or gneisses, and 

 crystalline limestone or marble. Areas of Grenville mappable as 

 such are much less conspicuous than in general throughout the Adi- 

 rondacks, the total of all areas represented on the accompanying 

 geologic map being only 2 or 3 square miles. 



Next in order of age comes the gabbro, commonly altered to 

 metagabbro represented by many small areas on the geologic map. 

 Most of this rock was certainly forced into the earth's crust after 

 the deposition of the Grenville strata and before the intrusion of 

 the syenite-granite series, but some of it is possibly of later age than 

 the syenite-granite. 



The greatest bulk of rock exposed within the quadrangle belongs 

 to the syenite-granite series, M'hich, in molten condition, was intruded 

 in vast quantities throughout the Adirondack region. Most of the 

 rock is granite, and the syenitic facies are generally rather quartz- 

 ose, in some cases varying to diorite. 



Many areas consist of mixed rocks, that is syenite-granite and 

 Grenville or gabbro so thoroughly and intimately associated as to 

 preclude separate mapping of these rocks. 



Pegmatite dikes, representing a late stage of intrusion or cooling 

 of the syenite-granite magma, are fairly common, though very few 

 are of considerable size. 



