lUi) if. p. CrSilTNG — Ar(JTE-SYEXlTE (.NKIt^S NKAJt LOON LAKE 



In the same report a number of pyroxeiiic gneisses are described as of 

 doubtful origin, and some of them may belong here, though the majorit.y 

 of them are clearl}^ referable to x\dirondack types, which have nothing 

 to do with the rocks under discussion * 



There are further described from many localities granitic gneisses -with 

 elongated <|uartzes, *' leaf gneisses," which seem in part identical wnth 

 those which appear in the Adirondacks associated with the syenite 

 gneisses as apparent extreme phases of th-e magmatic differentiation. 



LAKE XI FElilOIi 



Though the geological record preserved in the rocks of the Upper Lake 

 region is a much more complicated and complete one than that to be 

 read in the Adirondacks, still there is a close parallelism in the eruptive 

 rocks of the two districts, as has frequently been urged by N. H. Win- 

 chell. Similar syenitic rocks also occur there with the same close rela- 

 tionship to the gabbros, so far as can be told from the descriptions, and 

 have been described by Wadsworth and others. 



Kolderup has recently described exhaustive! 3" a most interesting series 

 of rocks which occur in the vicinity of Ekersund and Soggendal, in west- 

 ern Norway .f Unlike the other two Norwegian anorthosite areas, this 

 one has not suflfered regional metamorphism, so that the field relations 

 are exceptionally clear. He shows that the original magma of the dis- 

 trict has produced by differentiation anorthosite, norite and quartz- 

 norite, and tlie various members of the monzonite group (orthoclase- 

 plagioclase rocks), monzonite, banatite, adamellite, and granite. The 

 order of appearance, according to Kolderup, was first anorthosite, then 

 norite and monzonite, later adamellite and granite, and finally banatite, 

 with no considerable interval of time between any but the first and sec- 

 ond. Last of all and considerably later are dikes of diabase and augite 

 granite. All these rocks agree closely in their mineralogy with the Adi- 

 rondack eruptives. 



Sequence of Eruptions in the Adirondacks 



It is yet too early to attempt any complete discussion of the Adiron- 

 dack igneous rocks, and, owing to the excessive regional metamorphism, 

 it is an exceedingly difficult problem to work out the details of their 



* Ibid., pp. G7-82 



fCiirl Fred. Kolderup. Dd-^* lMl>radorfels i^ebjel; Ijtn Ekcisuiul uiul Sot^geodal, Borgei|s Mu- 

 seums Aarbog, l&OC), 



