64 Ailing — Problems of Adirondack Precambrian. 



been only slightly later in age than the anorthosite, seems 

 necessary. 



Bowen does not discnss the "Whiteface type of anor- 

 thosite, a rock studied and named by Kemp. In the Lake 

 Placid sheet the writer has found limestone-contact-zones 

 due to the igneous activity of the Whiteface (and pos- 

 sibly one due to the "Mt. Marcy") type of anorthosite. 

 This shows that mineralizers were not entirely lacking, 

 contrary to Bowen's conclusions. The age relations of 

 the two types, in so far as the writer knows, have not 

 been established. The writer's feeling is, however, that 

 we are dealing with two separate intrusives. 



In the Mt. Marcy sheet, on the west slopes of Baxter 

 mountain, large xenoliths of the Mt. Marcy type, highly 

 foliated, are engulfed in a mass of the same type of 

 anorthosite. A similar state of affairs is seen at Split 

 Eock Falls 36 in the Elizabethtown quadrangle, where a 

 peculiar type of rock is developed. How are we going 

 to interpret these observations and reconcile them with 

 Bowen's conclusions? 



The Gabbro. — Away from the large areas exposing the 

 Algoman gabbro this rock occurs as pipes and stocks. 

 This characteristic behavior is beautifully shown in the 

 North Creek sheet, as W. J. Miller has pointed out. But 

 on the Dixon-Faxon graphite properties at Graphite the 

 Algoman gabbro occurs as true inter- and intra-forma- 

 tional laccoliths — a most unexpected form of an igneous 

 mass. Swede Pond mountain seems to have been formed 

 by the injection and development of a laccolith beneath, 

 doming up the quartzite, so that distinct and opposite 

 dips are observable on the north and south slopes of the 

 hill. One small laccolith on the shore of North Pond is 

 just unroofed by the construction of a state road. 



The Term "Algoman". — The name Algoman, perhaps, 

 needs a word in the way of explanation. The term 

 "anorthosite-syenite-granite-gabbro series' ' is obviously 

 a clumsy expression. Miller has employed the term 

 syenite-granite in his writings. To those who have 

 followed the progress made by the Adirondack geologists 

 no confusion arises. But with the recognition of the old 

 granite, which Cushing regards as Laurentian, the need 

 for an analogous name to apply to the later series 

 becomes very desirable. "While it would have been more 



30 Kemp, J. F.: N. Y. State Mus., Bull. 138, p. 39, 1910. 



