

Carbonados in the State of Bahia, Brazil. 481 



The table following shows the order of the rocks, their 

 approximate thickness, and ages, in so far as the ages are 

 now known. In the adjoining state of Sergipe, Cretaceous 

 fossils have been found in abundance, and some have been 

 found in the vicinity of the city of Bahia, but below the Cre- 

 taceous nothing has thus far been discovered that makes it 

 possible to determine the ages of the beds with certainty.* 

 The divisions mentioned in this paper are based solely upon 

 stratigraphic and lithologic characters and physical breaks, 

 and must therefore be regarded as tentative until something 

 more trustworthy can be found. It should be added, however, 

 that these divisions when put to the test in the field appear to 

 be legitimate, and, for the most part, widespread. 



Table of Geologic Formations in the Interior of Bahia. 



Names Thickness in meters Ages 



Alagoas series _ ? Tertiary 



Sergipe series ? Cretaceous 



Salitre limestones ..350.. Jura ? 



Estancia red beds 350 Trias ? 



Lavras series (diamond bearing) 700 — Carboniferous 



Cambao quartzites 100. (possibly part of the Lavras). 



Caboclo shales (Paraguassu of 



Derby ?) 500 Devonian ? 



Jacuipe flints 100 (possibly part of the Caboclo). 



Tombador sandstones 400 Silurian ? 



Minas (or Jacobina) series 1 000 .. Cambrian ? 



Crystalline complex — Pre-Cambrian 



in part ? 



The Cambao quartzites and the Jacuipe flints appear to be 

 local deposits that may belong to the larger divisions either 

 above or below them. 



Attention is directed to the fact that the diamonds and car- 

 bonados are found in the Lavras series, and to the further fact 

 that the rocks of that series are everywhere of sedimentary 

 origin, strongly false-bedded, and for the most part gently 

 folded. The demarcation between the Lavras series and the 

 rocks above and below is clear and well defined, with the pos- 

 sible exception of places where the Cambao quartzites occur. 



Eruptives have been reported to me as occurring in the rocks 

 of the Lavras series only in the region south of the Serra do 

 Assurua about Fundao, and G-uariba. These rocks I did not 

 see personally, but they are reported by H. E. Williams, assist- 

 ant of the Servico Geologico do Brasil, who, as my assistant, 

 examined portions of the diamond regions. Mr. Williams says 



*It is reported that Carboniferous fossils were found in the interior of 

 Pernambuco in 1910 by Dr. Jose Bach, but I have not been able thus far to 

 get direct confirmation of the discovery. 



