ELIZABETHTOWN AND PORT HENRY QUADRANGLES 25 



In the Paradox Lake quadrangle which hes next south of the 

 EHzabethtown and also in the WhitehaU, which is southeast of the 

 Paradox Lake, there are extensive developments of a richly gar- 

 netiferous, green gneiss, often with much sillimanite. None of 

 this has been observed in the Elizabethtown-Port Henry area. 

 Its original is believed to be a somewhat calcareous shale and it is 

 characteristically associated with the graphitic schists or quartzites 

 which are the commercial sources of graphite. Its absence would 

 argue some change in the character of the Grenville sedimentation 

 to the north, presumably to more purely siliceous or feldspathic 

 materials, whose metamorphic derivatives lack both the lime and 

 the carbonaceous components. 



In addition to the above, which may be considered fairly well de- 

 fined sedimentary types, there are great masses of decidedly gneiss- 

 oid rocks, usually granitic or at least quartz-bearing in composition, 

 with hornblende and augite as the common dark silicates and with 

 coarse crystallization. They are well shown in the ridge of Bald 

 knob and they are extremely difficult to interpret. The writer's 

 disposition is, on account of mineralogical composition and associa- 

 tions to regard them as igneous in character. They are placed with 

 the syenite series as an acidic extreme. It is realized that another 

 observer might develop a strong argument for their sedimentary 

 characters. It is felt that the best course is to fully and fairly state 

 both cases hereafter. 



Chapter 4. 



GENERAL GEOLOGY [continued) 

 Metamorphosed eruptives 



This group is contrasted with the next one of the unmetamor- 

 phosed basaltic dikes, because the latter are obviously much later 

 and because they followed the period of metamorphism and crush- 

 ing, presumably also of extensive erosion, to which the former were 

 unquestionably subjected. At the same time it is believed that the 

 dikes are older than the Potsdam and that they belong to an en- 

 tirely different set from the ones which penetrate the Paleozoic 

 sediments^ in adjacent areas. 



The older eruptives with the possible exception of some ex- 

 posures of the basic gabbros constitute extended and huge masses 



1 See in this connection the following paper by H. P. Gushing who 

 was the first to show the distinction between the two groups. On the 

 Existence of Precambrian and Postordovician Trap Dikes in the Adiron- 

 dacks. N. Y. Acad. Sci. Trans. 1896. 15:248. 



