202 J. C. BRANKER AGGRADED LIMESTONE PLAINS, BAHIA, BRAZIL 



The OLD Catinga Limestone away from the Eailway 



Inquiries regarding the adjacent country point to the distribution of 

 this same limestone at about the same elevation both up and down the 

 streams crossed in this section of the railway, except that it does not ex- 

 tend up Eio do PoQO Comprido above Angico. It does extend down that 

 stream, however, and it extends both up and down the other streams, 

 especially along Eio Solidade. 



A trip made on horseback from the city of Joazeiro southwestward to 

 the Serra do Mulato, a distance of 41 kilometers, enabled the writer to 

 examine further this Catinga limestone in that direction. For several 

 leagues the road is nearly parallel with the Eio Sao Francisco. For the 

 first 2 or 3 kilometers it passes over the alluvial deposits of the river, 

 after which it passes onto granites, gneisses, and schists that are cut off 

 at the general level of the plain. Within the drainage basin of Eio 

 Salitre, at a distance of about 38 kilometers from Joazeiro, the road 

 passes onto the Catinga limestone. It here forms a horizontal sheet with 

 an etched or weathered surface. It is mostly gray to cream colored and 

 compact, like that at Carnahyba, and covers the high ground nearly to 

 Eio Salitre,^^ a distance of about 5 kilometers. Where the immediate 

 valley of the Eio Salitre cuts through the limestone, it is seen to be be- 

 tween 5 and 7 meters in thickness. At the Eio Salitre it rests immedir 

 ately on greenish talcose shales that stand nearly on end. On the west 

 side of that strearii the shales continue for a short distance up the imme- 

 diate valley side, but at the top of the ridge the limestones appear again 

 and continue as a thin de]30sit over the floor of the plain for some 15 or 

 20 kilometers. 



Figure 2. — Qeyieralized northeast-southwest Section, showing the Limestones as the 

 surface Rocks hetiveen Joazeiro and Rio Salitre 



I did not go much farther up this lower portion of the Eio Salitre than 

 Tapera, where it is crossed by the road from Joazeiro to Itumerim, but 

 two of my assistants, Messrs. Crandall and Williams, went to the falls 

 near Sargento, and they report that the Catinga limestone covers the high 

 floodplain on both sides of Eio Salitre as far as the Caxoeira do Salitre. 

 The section above will give an idea of the position and relations of the 

 Catinga limestone along the road leading from Joazeiro to fazenda 

 Itumerim. 



13 The rock at this place was noted by Spix and Martins, who speak of it as "a whitish 

 yellow dolomite in extensive beds, very little elevated above the general level," but they 

 say nothing further about it. Reise in Brasilien, vol. ii, p. 758. 



