1 86 EDWARD STEIDTMANN 



basalt and porphyry dikes. At Mineville, the syenites are associ- 

 ated with magnetite ores, which in their phosphorus content and 

 in the composition of their wall rocks resemble those of Kiruna. 

 The intrusive episode was followed by intense folding and Idng- 

 continued erosion. The Paleozoic rocks like those of Sweden were 

 here deposited upon an undulating floor of moderate relief. In 

 New York, evidences of old pre-Cambrian valleys filled by Pal- 

 eozoics have been found. The visible contacts between the pre- 

 Cambrian and the Paleozoic rocks in the Adirondacks as in Sweden 

 are partly depositional and partly along faults. 



The oldest pre-Cambrian rocks in the southeastern area of New 

 York are the Fordham gneiss, consisting dominantly of sedimentary 

 rocks intruded by granite batholiths. Kemp correlates the Ford- 

 ham gneiss with the Grenville series on the basis of lithologic 

 similarity, and identity of stratigraphic position. Above the 

 Fordham gneiss lie the Manhattan schists and Inwood marble, 

 both metamorphosed sedimentary formations, but less meta- 

 morphosed than the Fordham gneiss. They are intruded by 

 plutonic rocks showing a wide range of composition which show 

 parallelism to the Subjotnian of Sweden in their stratigraphic 

 relations, but not in their petrographic characteristics. The 

 Manhattan schists and Inwood limestones Kemp believes may be 

 parallel to the Huronian of the Lake Superior region and the 

 Jatulian of Sweden and Finland. 



KiimmeP states that the pre-Cambrian rocks comprise a series 

 of basic gneisses and limestones, which are cut by acid gneisses, and 

 pegmatites, all of which lie unconformably beneath the Cambrian. 

 The gneisses are nearly all mineralogically and chemically equiva- 

 lent to basic and acid igneous rock types, and are largely, if not 

 entirely of igneous origin. The acid intrusives present no evidence 

 of crushing, which probably means that their foliation was devel- 

 oped during crystallization by deformative stresses. The lime- 

 stones are associated with magnetite ores, and with the Franklin 

 Furnace and SterKng Hill zinc ores. The present state of crystal- 

 lization, and structural character of the rocks, as well as the develop- 



^ Henry B. Kiimmel, "Geological Section of New Jersey," Jour. Geo!., XVII, 

 No. 4 (1909), 351-80. 



