Lisboa — Permian Geology of Northern Brazil. 439 



seems to separate these two sediments, although it was not 

 possible to make any conclusive observations in this regard. 



In Grajahu the same gypsiferous limestone of Mearim out- 

 crops, but without the bituminous beds, which, if they occur at 

 all, are below the level of the river. It dips to the north - 

 northeast and is covered successively by red conglomeritic 

 sandstone and by quartzite. The strike is N. 60° W. Near 

 this place are the eruptions of trap already described. 



In the Grajahu river the gypsiferous limestone clearly dips 

 to the north-northeast and underlies the red sandstone sedi- 

 ments, supposed to be Triassic, which are cut by the amygda- 

 loidal diabase. It (the limestone) outcrops, showing a thick- 

 ness of twenty-five meters, near the base of a little chapada 

 capped by a red quartzitic sandstone which is supposed to be 

 the same as the Cretaceous sandstone of Torto. 



A bed of limestone bowlders apparently separates these sedi- 

 ments from the red sandstone. 



The notes of Baumann show that these bituminous and 

 gypsiferous shales are exposed under similar conditions in 

 Goyaz at the confluence of Rio Sereno with Rio Manoel 

 Grande on the Tocantins lowlands. 



Between Codo and the Barra do Corda are plains and low- 

 lands without topographic inequalities to facilitate geological 

 observations. 



In the lowlands the soil is usually covered by iron-cemented 

 rock, and since the character of the rains and the topography 

 are favorable to great annual floods, the ground is frequently 

 covered by alluvial detritus which prevents the observation of 

 the older sediments. For this reason the geological observa- 

 tions made in this region are but scanty. 



The following observations seem to merit mention, however. 



The road from Codo to Barra do Corda, after crossing the 

 bituminous shales, continues, between Fazenda Uniao and Boa 

 Esperanca on a lower white sandstone, immediately underlying 

 the bituminous shales. From Boa Esperanca to the village of 

 Pao Douro, a two days' journey, is a hopeless traverse for the 

 geologist. There is only bog iron ore and sandy soil without 

 rock outcrops. The road climbs to the village of Pocos, the 

 white sandstone disappearing and being succeeded by a red 

 sandstone in the form of bowlders in the soil, but showing good 

 stratification. The ground there begins to be broken by table- 

 topped hills. The sediments are soft. The land continues to 

 rise, but always gradually, to Cruzeiro, and beyond to the 

 Serra da Boa Vista. The Serra da Boa Vista is the edge of a 

 plateau which continues to the flanks of Almeida on the 

 Itapicuru. 



With a fall of about 100 meters the road descends along the 

 steep edge of the plateau toward the village of Pocos, which 



