170 C. SCHrCHERT THE NORTH AMERICAN GEOSYXCLIXES 



111 the PennsylYania-MarYland area thev make up the Glenarm series, 

 and in Xew York the equivalent formations are the Lowerre, Inwood, and 

 Manhattan (Jonas). The thickness is something like 10,000 feet. 



In ISJ'oYa Scotia the Gold-bearing series consists of a lower quartzite 

 gronp abont 11,000 feet thick and an npper graphitic and ferniginons 

 slate group about 4,000 feet in depth. 



In southeastern Newfoundland the Proterozoic series is over 11,000 

 feet thick, and consists of coarse qnartzites, slate conglomerates, slate, 

 and diorites. 



The Ontarian geosj^ncline (so named because best developed in Ontario 

 Province) embraces the Animikian, or Iron series, of but little disturbed, 

 dark, carbonaceous (6-10 per cent) slates and sandstones, with iron- 

 bearing chert and jasper and impure limestones and dolomites. In the 

 Penokee area of Michigan the portions remaining have a thickness of 

 11,000 feet, but elsewhere they are much thinner. These strata are held 

 to be of marine origin. 



The Animikian series is followed by the Keweenawan sediments, usually 

 of a red color, and metal-bearing volcanics (seemingly plateau flows, 

 largely diabase and basalt). In the Lake Superior region the lower 

 conglomerates and sandstones, with impure limestones and shales, have 

 a thickness of from 300 to 1,400 feet. They may be of marine origin. 

 Then comes the middle series, probably wholly of continental origin and 

 upward of 30,000 feet thick, of which at least five-eighths is igneous 

 material, the rest being red conglomerates and sandstones. The upper 

 series attains localh^ to 20,000 feet, most of which is sandstone of fresh- 

 water origin, derived from the volcanics. 



The Ontarian geosyncline is the oldest known trough of Xorth America. 

 It probably had its origin during Archeozoic time, since all of the older 

 Proterozoic deposits, and even the Grenville series of Ontario, likewise 

 have the alignment of the younger series. 



The greater Arctic sea is not regarded as a true geosyncline. The 

 sediments are largely sandstones, with some slate. It is interesting to 

 note this late Proterozoic marine invasion, since it recalls the four similar 

 floods of Ordovician and Silurian times. 



DeVELOPMEXT OE THE APPALACHIAX GeOSYXCLTXE 



(See Maps. Figures 4 to 12) 



GEOSTXCLIXES IX GEXERAL 



In Xorth America the geosynclines all lie on the inner or continental 

 side of borderlands (see map, figure 3). Their • deposits are thickest 



