4:36 Lisboa — Permian Geology of Northern Brazil. 



at Caieira, station of Aarao Reis on the Caxias-Cajazeira rail- 

 way, which I correlate with that of Gangorra. It is in the 

 same Permian zone of abundant silicifications of Psaronius, 

 and it is noteworthy for having its surface eroded at the con- 

 tact with the overlying sediments, as I was able to verify in a 

 recently opened quarry. This shows a long period of erosion 

 before the deposition of the overlying beds. 



At Caieira this limestone marks a genuine nonconformity 

 and must represent the top of the Permian. The overlying 

 sediments are red clays which alternate with white sands that 

 extend to the coast and are supposed to be of Cretaceous or 

 Tertiary age. 



At Gangorra the top of the limestone was not seen in con- 

 tact with the upper sediments that seem to overlie them con- 

 formably and which are the Cagado sandstones on top and 

 Croata sandstones beneath. 



The Cagado sandstone. — The Cagado sandstone is rather 

 thick and uniform in appearance. In the latitude of Pastos 

 Bons it forms the middle parts of the plateau escarpments on 

 the sides toward the Parnahyba. It is everywhere marked by 

 peculiar big white and red splotches that characterize the limits 

 between the upper Permian and the lower Triassic of Brazil. 

 Dr. I. 0. White mentions this peculiarity of the sediments of 

 Bio do Rasto, which he regarded as of lower Triassic age. 

 The repetition of this phenomenon in northern Brazil in the 

 sediments overlying Permian beds containing Psaronius just 

 as they do in southern Brazil, is worthy of note. Some years 

 ago I saw the same phenomenon in still another remote region 

 in Brazil almost at the base of the escarpment of the Triassic 

 plateau of Matto Grosso in the valley of the Aquidauana. 

 Those sediments I now recognize as probably synchronous 

 with those of Cagado in Maranhao, and with those of Rio do 

 Rasto mentioned by I. C. White in southern Brazil. 



The Cagado sediments extend throughout the basin of the 

 Itapicuru in the latitude of Mirador. 



The Croata sandstone. — Above it is a rose-colored sandstone 

 spotted with white and even grading into white with intercala- 

 tions of shales which make a yellow clayey soil. This varie- 

 gated rose-colored sandstoue is well exposed in the village of 

 Croata. 



The Mearim Series (Triassic ?). 



The upper beds are composed principally of red sandstone 

 and include flows of amygdaloidal trap. These are probably 

 synchronous with the beds which Derby has considered Triassic 

 in S. Paulo and Parana, and which I. C. White regarded as 

 the upper member of the S. Bento series in his Santa Cathe- 



