Lisboa — Permian Geology of Northern Brazil. 433 



was seen over a large area in the vicinity of that city occur- 

 ring not only above Grajahti but also in the divide between 

 the Itapicuru and Tocantins rivers, near Carolina on the Tran- 

 queira river. This type of eruptive also appears in the high 

 divides between the Mearim and the Corda and between the 

 Corda and the Alpercatas. It forms sheets between beds of 

 red sandstone, correlated in his paper with the Triassic as was 

 done in the south. In no part of the north of Brazil have 

 eruptives been seen cutting Cretaceous sediments.* 



Siliceous beds^pisolitic sandstones and cherts. — Pisolitic sili- 

 ceous formations occur among the upper Permian sediments. 

 There are also opal beds in the limestones and the argillaceous 

 shales which underlie the Psaronius sandstones. These sili- 

 ceous rocks, accompanied by the disintegrated material of the 

 rocks which contain them, are scattered in the form of bowld- 

 ers over the surface of large areas, giving a reasonably safe 

 indication that they are derived from definite sediments. The 

 same thing happens in the case of certain siliceous concentrations 

 (silicate of iron?), light green in color, from the amygdaloidal 

 eruptive rock, which either form, as bowlders of decomposition, 

 a surficial bed over large areas, or else separate the eruptive 

 from the overlying sandstone. 



Such occurrences have not been found in the Cretaceous 

 sandstones. The Cretaceous sediments in northern Brazil are 

 essentially sandy, and as they approach the Triassic and the 

 Permian they become more and more clayey. 



The facts to which I have referred, and the study of the 

 geology along certain sections, made it possible to separate for 

 the first time the geologic sediments of northern Brazil in the 

 states of Maranhao, Piauhy, and Goyaz. 



The Permian and Post-Peemian Rocks. 

 The discovery of Psaronius in the states of Maranhao, 

 Piauhy, and Goyaz, and of fossil dicotyledonous plants in 

 Maranhao, permits the identification of extensive beds of a 

 great system of sediments in the north of Brazil. In the ab- 

 sence of paleontologic evidence, the post-Permian or pre-Cre- 

 taceous beds could only be separated with much uncertainty. 

 The characteristic features of the rocks of one series and their 

 analogy with the sediments of southern Brazil led me to refer 

 it to the Triassic. 



Upper Permian Pamahyba Series. 



The Permian sediments with Psaronius were first identified 



by me in the plateau of Jaboti and in a little brook known as 



* The sedimentary beds of the Abrolhos covered by eruptives were referred 

 by Hartt to the Cretaceous. There is no certainty, however, about the age 

 of the Abrolhos beds. — J. C. Branner. 



