158 



A. Wandke — Intrusive Rocks. 



Correlation of the Intrusives. 



Alkaline rocks were at one time regarded as rare in 

 New England, but little by little new localities for the 

 occurrence of these types are being reported. The 

 subjoined table notes some of the localities in New 

 England from which alkaline rocks have been reported 

 and also shows the approximate ages of the intrusives. 



Localitj. 



Mt. Ascutney, 

 Vermont. 



Cuttingsville, 20 

 Vermont. 



Litchfield, 21 

 Maine. 



Belknap Mountain, 22 

 New Hampshire. 



Types of Intrusives. Age. 



Biotite granite, nord- Post Carboniferous and 

 markite, pulaskite, pre-Cretaceous. 

 diorite, essexite, gab- 

 bro, paisanite. 



Essexite and nepheline Age unknown, 

 syenites. 



Syenites and nepheline Age unknown, 

 syenites. 



Syenite and aplite. 



Tripyramid Mountain, 23 Monsonite and syenite. 

 New Hampshire. 



Blue Hills, 24 

 Massachusetts. 



Copper Mine Hill, 2 

 Ehode Island. 



Essex County, 26 

 Massachusetts. 



Portsmouth Basin, 

 Maine and New 

 Hampshire. 



No age given. 

 No age given. 



Upper Carboniferous. 

 Middle Devonian. 

 Middle Pennsylvania!!. 



Alkali-granite. 



Quartz diorite and bio- 

 tite granite. 



Eiebeckite-aegerite 

 granite. 



Diorite, calci-alkaline 



granite, grano-dior- 



ite, gabbro diorite. 

 Alkaline syenites, Cape 



Ann and Peabody 



granites, Andover 



alkaline granite. 



Biotite granite. 



Quartz diorite, biotite 

 granite, gabbro, 

 grano-diorite, alka- 

 line granite, alkaline 

 syenite, gabbro? 



Foxgrove House, Cambridge, Mass. 



19 E. A. Daly, U. S. Geol. Survey, Bull. 209, 1903. 



20 J. W. Eggleston, this Journal, vol. 45. 1918. 



21 E. A. Daly, Bull. Geol. Soc. Amer., vol. 29, p. 463, 1918. 



22 L. V. Pirsson, this Journal, vol. 22, 1906. 



23 L. V. Pirsson and W. N. Eice, this Journal, vol. 31, 1911. 



24 C. H. Warren and S. Powers, Bull. Geol. Soc. of Amer., vol. 25, p. 463. 

 23 C. H. Warren and S. Powers, ibid. pp. 452 and 463. 



20 C. H. Clapp, U. S. Geol. Survey, Bull. 704, 1921. 



Post-Ordovician and pre- 

 Silurian ? 



Mississippian or Pennsyl- 

 vania!!. 



Pre-Carboniferous. 

 Post Upper Carbonifer- 

 ous. 



