370 E. C. HARDER AND R. T. CHAM BERLIN 



before the incursion of the early Devonian sea. In Sao Paulo and 

 Parana, the basal beds of the Devonian (which have been assigned 

 to Lower Devonian) rest unconformably on a westward dipping, 

 now slightly warped surface of these old deformed rocks in such a 

 manner as to show that the sea crept in over a region of little or no 

 relief.^ An interval of much erosion is therefore implied. 



The location and trend of these mountain ranges is worthy 

 of note for their bearing upon the major problem of earth move- 

 ments and deformation. It is no new fact that the ranges of 

 eastern Brazil are rather strikingly parallel to the border of the 

 continent, and not far back from the coast. In Minas Geraes the 

 repeated overthrust faulting has nearly all come from the southeast. 

 The strata of the faulted slices nearly always dip toward the 

 Atlantic. The picture of the Atlantic Ocean segment crowding 

 the eastern side of the South American continent, squeezing it 

 and forcing it upward like a triangular wedge and wrinkling and 

 slicing the edge comes very appealingly to mind. At a later time 

 the Pacific Ocean segment seems to have done the same on that 

 side. 



PALEOZOIC — EARLY MESOZOIC EROSION PERIOD 



After the great period of mountain-building we have evidence 

 only of a long period of erosion whose final result was to develop 

 an approximate base-level which is, at present, only preserved on 

 the crest of the Serra do Espinhafo. The amount of material 

 removed from the upthrust blocks was great, suggesting that the 

 interval between the end of the deformation and the completion of 

 the base-level was a long one. The process of base-leveling was 

 probably not rapid, since the hard Caraga quartzite is a very resist- 

 ant formation and would have been reduced slowly. That the 

 process progressed nearly to completion is evidenced by the char- 

 acter of the crest of the Serra do Caraga which, even today, pre- 

 serves in places a well-developed plain (Fig. 8). The Serra do 

 Caraga being composed of more resistant rock than the surround ng 

 region, this quartzite area would be the last portion of the region 

 to be brought to base-level. As the upturned Caraga strata were 



'J. B. Woodworth, "Geological Expedition to Brazil and Chile, 1908-9," Bull. 

 Mas. of Compar. Zool. Harvard College, LVI, 42. 



