8 SOPER— GEOLOGY OF PARAHYBA 



throughout the crystallme areas of Parahyba and Rio Grande do 

 Norte. 



The sedimentary series, as previously indicated, may be sepa- 

 rated into three divisions. First, there is a bed of rather coarse- 

 grained and sometimes conglomeritic sandstone which directly over- 

 lies the crystalline rocks. In color it is usually brick-red but may 

 also be yellow or white. The color is probably due to varying 

 amounts of iron stain. The contact between this sandstone and the 

 crystalline rocks was first seen where it crosses to the southeast side 

 of the Rio Jaguaribe, a few kilometers to the south of Limoeiro. 

 From there it passes close to the village Taboleiro d'Areia and con- 

 tinues to follow the general direction of the Chapada do Apody, 

 but about 9 kilometers back to the southwest of the Chapada, until 

 it reaches Passagem Funda. At this point the contact is 15 kilo- 

 meters to the south. From here it continues to follow the direction 

 of the escarpments of the Chapadas Sao Sebastiao and Vacca IMorta, 

 always from 8 to 12 kilometers to the south of them. These last two 

 named escarpments are in reality only a continuation of the scarp of 

 the Chapada do Apody. At Assii the contact passes almost through 

 the city and from there on to Natal it is very regular, always approach- 

 nearer to the coast as we go south. It passes very close to the village 

 Garapeba, and to the railway station Baixa Verde, passes just north 

 of Taipu, south of Ceara Mirim, and is seen about 5 kilometers west 

 of Macahyba. From this point south it is noted a few kilometers 

 west of S. Jose, passes through Curimatu, goes close to Espirito 

 Santo, and Pedra de Fogo. Thus the sandstone is exposed in a nar- 

 row strip from near Aracaty, at least to Natal and probably on down 

 into the state of Pernambuco. A section at right angles to its length 

 would show a consistent width of exposed area from 8 to 12 kilo- 

 meters. The only reliable structure that I have seen in this rock was 

 in the vicinity of Apody, along the escarpment of the Chapada do 

 Apody, and near Assu, along the Lagoa Piato. In these places the 

 sandstone beds dip from 3 to 8 degrees to the northeast or toward 

 the sea. There are some good exposures near Garapeba also, but 

 little structure is evident there. For the most part the exposed 

 sandstone is seen on the surface as an incoherent, heavy, yellowish- 



