1 84 EDWARD STEIDTMANN 



sediments of the sand clay type, the other to both dynamic and 

 contact metamorphism. 



Bayley^ states that the pre-Cambrian of New Jersey consists 

 essentially of three series of gneisses, sodic, potassic, and basic, 

 respectively, accompanied by pegmatites, all intrusive into still 

 older limestones, the Franklin limestone. The gneisses contain 

 magnetite ores in form pod shaped, northeastward-pitching shoots 

 having the same structural attitude as the gneisses, and are fre- 

 quently offset by cross and longitudinal faults. The ores are 

 titaniferous, and are associated with basic and alkaline silicates. 

 The Franklin limestone also contains some magnetite ores. These 

 are non-titaniferous, veinlike masses, associated with heavy lime 

 silicates and calcite. 



Gushing^ et al. state that the pre-Cambrian succession of the 

 Thousand Islands' region may be classified, beginning with the 

 oldest, as: (i) Grenville metamorphosed sediments, consisting of 

 marbles, schists, gneisses, quartzites which originally were sand- 

 stones, shales, and limestones; (2) granite gneisses intrusive into 

 the Grenville, and which have changed the Grenville into amphib- 

 olites along the contacts; (3) small bodies of massive syenite, 

 gabbro, and granite;, (4) unmetamorphosed basic dikes. 



This region shows less complexity of folding, a greater dominance 

 of acid intrusives, and fewer basic igneous rocks than the northern 

 Adirondacks. It is regarded as a transition between the Adiron- 

 dacks and the Grenville area of Canada. • 



Dale and Gregory'' state that the Becket granite gneiss of 

 probably pre-Cambrian age outcrops over wide areas in northern 

 Litchfield county, Connecticut. 



Emmons and Laney* state that the pre-Cambrian in the Duck- 

 town district consists of the Carolina gneiss, a series of gneisses 



' W. S. Bayley, "Iron Mines and Mining in New Jersey," Geol. Survey of New 

 Jersey, Vol. VII, 499 pp., 23 pis., 2 maps, 31 figs. 



^ H. P. Gushing, H. L. Fairchild, R. Ruedmann, and C. H. Smith, Jr., "Geology 

 of the Thousand Islands' Region," New York State Mus. Bull. 145, 194 pp., 63 pis., 6 

 maps, 9 figs., 1910. 



3 T. Nelson Dale and Herbert E. Gregory; "The Granites of Connecticut," Bull. 

 484, U.S. Geological Survey, 1911. Several maps. 



4 W. H. Emmons and F. B. Laney, "Preliminary Report on the Mineral Deposits 

 of Ducktown, Tennessee," Bull. 470, U.S. Geological Survey, 1910. 



