Lisboa — Permian Geology of Northern Brazil. 441 



minous shales of Codo, and the occurrence of the same fossils 

 at the Barra do Corda,* where the same beds outcrop, support 

 this theory. Our preliminary studies lead us to conclude that 

 the bituminous shales of Codo, of the Barra do Corda and of 

 Manoel Alves in the Tocantins lowlands are to be correlated 

 and represent the same Permian horizon throughout northern 

 Brazil. If these assumptions prove to be correct, the bitumi- 

 nous shale is a base of reference in north Brazil as important 

 as the Iraty shale in the south. 



If the information given me can be depended upon, the 

 shales crop out also in the interior of Piauhy on the flanks of 

 the plateaus that drain toward the Parnahyba between the 

 municipalities of Floriano and Therezina. These statements 

 can only be verified by later studies. 



When I went up the Itapicuru, I observed from the steamer, 

 at Manso da Marianna, a big escarpment on the right bank of 

 the river where I thought I could recognize an unconformity. 

 The banks of the river are of sandy and clayey rocks, always 

 red and ashen gray but free from alluvial sand. These sedi- 

 ments are horizontal, but in the river bank at Manso the lower 

 bed seems to show an erosion surface at the contact with the 

 upper one. A detailed examination would perhaps permit the 

 recognition there of the contact of the Cretaceous or Tertiary 

 beds of the coast with the pre-Cretaceous or Permian of the 

 interior. 



Independent of these observations on the banks of the Itapi- 

 curu at Manso, we know that, in accordance with facts stated 

 above, and the occurrence of fossil dicotyledons with Psaronius 

 in the Parnahyba valley, the Cretaceous rests directly on the 

 Permian in the eastern part of Maranhao. The occurrence 

 in the region described of bituminous shales at the base of 

 the Cretaceous of northern Brazil (Araripe) renders possible the 

 theory of two bituminous formations, one belonging to the 

 lower Cretaceous, the other to the Permian. This plausible 

 hypothesis introduces further doubt in regard to any method 

 other than paleontologic for the determination of the ages of 

 these sediments. 



Geographical Limits or the Permian and Triassic. 



From the notes of my assistant, Mr. Baumann, we have seen 

 that we can safely extend the limits of the Permian from .the 

 south of Maranhao to Porto ]STacional in Goyaz. In the upper 

 Parnahyba these sediments occur at the headwaters of the 

 Balsas. 



Through the geological studies of Dr. Roderic Crandall we 

 can now identify with the series of the Parnahyba the greater 

 part of the sediments of Piauhy between Floriano and Picos. 



* J. C. Branner, Geologia Elemental - , p. 246. 



