GENERAL AND ECONOMIC GEOLOGY 237 



Tertiar}^ and which extends from the vicinity of the city of Bahia to and 

 across the Eio Sao Francisco above the falls of Paulo Affonso. The Per- 

 mian rocks have not been recognized as snch elsewhere throughout this 

 entire zone, but it is assumed that they are continuous, and they are so 

 represented on the map. N'owhere else in Bahia have the Permian rocks 

 been certainly recognized. 



In the Salitre Valley and over wide areas in the country north of 

 Lavras the map shows limestones which are referred doubtfully to the 

 Permian. These limestones have yielded no fossils, with the possible 

 exception of some algse that have thus far baffled all attempts at deter- 

 mination. The age of the beds is therefore in doubt. In some places 

 they seem to rest unconformably against the diamond-bearing quartzites 

 referred to the Carboniferous. It is not at all clear, however, that these 

 limestones are all of the same geologic age. 



Cretaceous rocks are exposed at many places about the Bay of Bahia, 

 on the east side of the island of Itaparica, at Marahu, and at many places 

 through the zone of sedimentary rocks that extends from Bahia north- 

 ward to near Jatoba, on the Eio Sao Francisco. At Marahu and about 

 the Bay of Todos os Santos fossils have been found, and there is no ques- 

 tion about the age of certain rocks. All of the sedimentary rocks there- 

 about are not Cretaceous, however, as seems to be inferred occasionally, 

 for there are at many places remnants of the Tertiary beds, most of which 

 have been completely removed by denudation. On the island of Itaparica 

 Dr. Eathbun recognized Tertiary beds on the west side of the island; at 

 Monserrate, in the suburbs of Bahia, brackish water fossils are found 

 that are certainly Tertiary,*^ and in some of the railway cuts northwest 

 of Alagoinhas Tertiary plant remains are abundant in sediments overly- 

 ing unconformably the Cretaceous beds^^ at kilometer 28+. 



Any one who undertakes geologic or paleontologic work in the vicinity 

 of the Bay of Bahia should not fail to read the paper by Joseph Mawson 

 published in the Geological Magazine of August, 1913, pages 356-361. 

 Mr. Mawson lived at Bahia many years, and it is to him that we owe the 

 valuable collections of Cretaceous vertebrate remains described by Dr. 

 A. Smith Woodward. 



Along the coast, both north and south of Bahia, is a narrow belt of 

 Tertiary sediments that lap back over the older formations. This belt is 

 cut through here and there by the drainage, and where the sea has under- 

 cut the beds they form the particolored cliffs that characterize this part 



^■^ See Chas. A. W'hite's Contributions to the Paleontology of Brazil. Archivos do 

 Museu Nacional, vii, p. 233. 



*8 F. Krasser : K. von. Ettingshausen's Studien uber die fossile flora von Ouricanga in 

 Brasilien. Sitz. der K. Akad. d, Wiss. Wien., cxii, 1903. 



XVII— Bull. Geol. So^c. Am., Vol. 30, 1918 



