REPORT OP THE DIRECTOR AND STATE GEOLOGIST 1900 r61 



and makes the acute suggestion that it probably belongs in the 

 general eruptive series with the Whitehall augite syenite gneiss. 

 This is precisely the same gneiss as that described from and about 

 Piercefield in the present report. It is also the same gneiss as 

 that about Lake Marian, where it is associated with a magnetite 

 ore body and with supposed Grenville rocks. Though the writer 

 ie in doubt as to its precise relations, his inclination is to refer 

 it to the general eruptive series, as Kemp does. 



To summarize, Kemp reports large bodies of syenite and 

 granite, mostly gneissoid, whose eruptive origin is distinctly 

 stated, which are, by implication at least, younger than the G-ren- 

 ville series, but whose relationship to the anorthosite there is no 

 opportunity for determining. 



Smyth's report deals largely with an area of augite syenite in 

 the western Adirondacks, the Dlana-Pitcairn area, in which most 

 interesting and important observations were made and recorded. 

 In this area again, however, the absence of anorthosite precludes 

 any determination of the relations of the two eruptives. But, 

 on the other hand, the rock, variable here as elsewhere, is shown 

 to have an important gabbro facies, and to pass locally into a 

 gabbro. 



The evidence detailed in the report shows in the clearest man- 

 ner that the syenite cuts the Grenville rocks irruptively and is 

 therefore younger, the widespread character of the Grenville on 

 the northern border of the syenite giving exceptional opportunity 

 for such determination. It also shows that on the south the 

 syenite boundary is not clearly defined, but that it apparently 

 passes over into a granitic gneiss, and Smyth had previously 

 shown a definite transition of the sort, west of Natural Bridge in 

 Jefferson county .^ Farther to the south, he shows the presence 

 of a different granite, usually gneissoid, which he is in doubt 

 whether to regard as a derivation product of the syenite or as 

 representing a separate intrusion, but which in either case 

 emphasizes their close relationship. He also remarks the wide 

 distribution of such granitic gneisses in the southwest 

 Adirondacks. 



* Geol. soc. Am. Bui. 6 : 282-83, 



