Chart i 





1^ >"\ | 



Precambric 











Algonkic 





iiil i 





Metamorphosed 

 Paleozoic 











Cambro- 

 Ordovicic 







« 







Siluric 





W//A 





Devonic 





111 11 



Mississippic 



GEOLOGICAL SKETCH MAP OF THE EASTERN UNITED STATES 



MN southern boundary of Canadian shield A. D a and E a the symmetric Isles Wisconsin and Adirondack D, and E.'the adioinine marginal de 



Z™° of el- ^ b D5 " D3 n 8U c e Jine ° £ WeStem 3rm ° £ P ' atf0rm - Ea " Es that ° f the CaStem arm - D > Isle O^rk! E 3 I'sle App cw" b7b7 u de 

 line of ax ls of eastern basin. B, Cincinnati geanticline. B, Michigan basin. B 3 and B, symmetric subbasins 



