84 EDWARD STEIDTMANN 
Fenner™ advocates the theory of the origin of certain gneisses 
by injection. 
Katz? tentatively assigns certain quartzites, slates, and schists 
of southwestern Maine to the Algonkian because of their lithologic 
resemblance and area and structural relationship to the Westboro 
quartzite and Marlboro formation of eastern Massachusetts. 
Keith’ has traced an unconformity at the base of the Cambrian 
along the west border of the Green Mountains, and concludes that 
certain older sediments beneath the unconformity are properly 
classed as Algonkian. 
La Farge and Phalen‘ follow Keith in placing the Ocoee group 
of the southern Appalachians in the Cambrian. In the Ellijay 
quadrangle of northern Georgia they recognized several groups of 
pre-Cambrian rocks, all of which they classify as Archean. 
_ The most abundant types comprise an older complex of acid 
schists and gneisses whose origin is doubtful, and a younger group 
of areally less extensive basic gneisses and schists, mostly dioritic 
gneiss which is intrusive into the older complex. The first is known 
as the Carolina gneiss, the latter as the Roan gneiss. Intimately 
associated with the Roan gneess, are small masses of pyroxenite and 
dunite which are probably intruded into the Roan gneiss. Both the 
Roan and the Carolina gneiss are intruded by small masses of granite 
believed to be Archean in age. 
Martin’ recognizes a Grenville series and post-Grenville in- 
trusives in the Canton quadrangle of northern New York. The 
Grenville includes limestones, garnet, and siliceous gneisses, 
quartzites and quartz schist and amphibolite. The post-Grenville 
tC. N. Fenner, ‘Mode of Formation of Certain Gneisses in the Highlands of 
New Jersey”’ (Abstract), Geol. Soc. Am. Buil., Vol. XXV, No. 1 (March 30, 1914), 
Pp. 44-45. 
2F. J. Katz, “Stratigraphy in Southwestern Maine and Southeastern New 
Hampshire,” U.S. Geol. Surv., Prof. Paper 108 (1918), pp. 165-77. 
3 A. Keith, ““A Pre-Cambrian Unconformity in Vermont,” Geol. Soc. Am. Bull., 
Vol. XXV, No. 1 (1914), pp. 39-40. 
4L. La Farge and W. C. Phalen, “Georgia, North Carolina, Tennessee,” Ellijay 
Folio, No. 187 (1913), 17 pp-, 4 maps. 
5 James C. Martin, ‘“‘The Pre-Cambrian Rocks of the Canton Quadrangle,’’ 
New York State Mus., Bull. No. 185 (1916), 112 pp., 20 pls., 31 figs., maps. 
