STRATIGRAPHIC GEOLOGY 



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gneisses and granites. The result is a section somewhat like the ones 

 here shown, bnt varying according to the angle of the fault-plane, the 

 amount of the thrust, etcetera. These early Paleozoic beds are thus 

 brought into intimate relations with the Archean rocks, and it seems 

 quite probable that the high metamorphism and the presence of so many 

 characteristic and valuable minerals may be due, in part at least, to these 

 relations. The dips of the beds are generally high, and not infrequently 

 the beds are nearly or quite vertical. The statement is sometimes made 

 that the dip is always toward the east,* with a rugged outcrop on the west ; 



Figure 1. — Theoretic Structure of ThrHst-faiilting of earJi/ Paleozoic into the Archean 



this is locally, and only locally, true. In the State of Bahia the Serra de 

 Jacobina, which belongs to this series, dips about 60 degrees toward the 

 east (with slight variations) along its entire length — a distance of 225 

 kilometers. 



In the State of Minas Geraes, where the early Paleozoic beds have been 

 most studied and written about, the direction and angle of the dip varies 

 much, and the sequence of the beds is variously stated by different writers. 



I have here brought together the sequence in Minas Geraes as given 

 by eight different geologists : 



ESCHWEGE, 1831 



(Gebirgskunde Brasiliens) 

 Uebergangsthonschiefer 



Claussex, 1841 

 (Acad. Roy. Bruxelles, volume YIII) 

 Terrain transition 



Eisenglimmer 

 Itacolumite-quartz 

 Urthonschiefer 

 Kornquartz 



Granite-gneiss 



Traumateux 

 Itacolumite 

 Micacique 

 Quartzitique 



Granite-gneiss 



*Heusser u. Claraz : Zeit. Deut. Geol. Gesell., vol. xi, p. 451. Berlin, 1889. 

 XV — Bull. Geol. Soc. Am., Vol. 30, 1918 



