210 Annals of the Carnegie Museum. 



sandstone seems to overlie the schists, its thickness, where observed, 

 being not over one hundred meters. In a number of places there are 

 masses of crystalline limestone. It is not evident whether or not 

 these masses represent a regular bed, but it seems more probable that 

 the limestone is present as lenses, at about the same geologic horizon 

 in the series. The" rocks are greatly jointed, but do not exhibit much 

 folding or crushing. Where the schists exhibit shearing they have 

 been hardened, so as to form resistant layers which rise above the 

 general level. Many irregular dikes of pegmatite and other acid 

 rocks have been injected into the schists. 



To the quartzite, crystalline limestone, and schists should probably 

 be added shales, good exposures of which were seen by SmalP^ in the 

 extreme southern part of Ceara. 



Small says of the schists that.it is in most places difficult to dis- 

 tinguish between those of the Ceara Series and the crystalline schists 

 of the basement complex; but that the former seem to be softer and 

 more argillaceous and to disintegrate more readily to soil. In some 

 places in the Ceara Series mica-schists and rocks rich in manganese 

 and iron predominate, and amphibolite-schists are also common. 



Soper says: ^^ "The Ceara Series, where it is distinguishable, seems 

 to be composed of acid rocks, usually of a light color. They con- 

 tain more or less kaolin and clay and in some cases have a peculiar 

 earthy appearance. On weathering off they do not weather into 

 rounded boulders with smooth surfaces, but outcrop in jagged ex- 

 posures, and the boulders, large and small, have sharp edges — not 

 rounded ones. The Ceara Series usually presents a schistose appear- 

 ance and in places according to Mr. Crandall, may contain lenses of 

 hard, vitrified sandstone. In other places there are masses of lime- 

 stone completely isolated in areas of schist. However, there does 

 not seem to be any systematic separation of this series from the 

 other rocks and it is often, if not usually, impossible to make any 

 distinction at all." 



Wherever the Ceara Series was definitely recognized by the -writer, 

 by the presence of quartzite or of crystalline limestone, the general 

 characteristics of the associated schists, as given by Crandall, Small, 

 and Soper, were noticed. The impression obtained by the writer was, 



2* Publ. No. 25 of the Inspectoria, pp. 49-41, and Photograph No. 21. 

 '^ The Geology of Parahyba and Rio Grande do Norte, Brazil, by Ralph H. Soper, 

 Proc. Am. Phil. Sac, Vol. LV, No. i, 1916, p. 7. 



