CRYSTALLINE AND SALTTRE LIMESTONES 189 



The present paper is chiefly concerned with the Catinga limestone, but 

 a few words concerning the older ones are necessary in order to make 

 clear their important relations to the later limestones of the same region. 



Crystalline Limestones 



The white crystalline marbles have been seen at only a few points on the 

 Sao Francisco Eailway at and about kilometer 434 (from Alagoinhas). 

 Here the marble has been quarried from several pits, where it is inter- 

 bedded with qnartzites and associated with schists. It is quite probable 

 that the limestones of this period are not uncommon through the region 

 of crystalline rocks, but this is the only place at which they were seen in 

 the State of Bahia. Similar marbles have been seen at Sao Caetano and 

 near x\guas Bellas, in the State of Pernambuco,^ and at all of these places 

 they are associated with very old metamorphic rocks that are here referred 

 tentatively to the pre-Cambrian. 



The Salitre Limestones 



The Salitre limestones and marbles are the most important rocks of the 

 kind in the State of Bahia. They vary greatly in character, color, and 

 thickness ; they present a wide range of structural features, and they cover 

 large areas in the northern and western portions of the State, possibly as 

 much as 50,000 square kilometers. Toward the southern end of the 

 Salitre Valley, especially south of Tabua, these limestones are beautiful 

 pink and red marbles. Similar red marble was found on the plateau, 14 

 kilometers west of Eio Jacare, on the road from Jacare to America 

 Dourada. As indicated in the table, paleontologic evidence of the age of 

 these beds is thus far lacking, and that, too, in spite of constant vigilance 

 and the most careful search for fossils at a large number of excellent 

 exposures. .The only fossils found thus far are small pellet-like algae, tliat 

 are quite abundant at many places, especially at Carahyba, about America 

 Dourada and north of there in the drainage basin of the Rio Jacare. 

 These nodules are from less than 1 millimeter to 6 millimeters in diame- 

 ter, and at many places they are so abundant as to form the mass of the 

 rock. 



Microscopic slides were made of the material, and they were submitted 

 to Dr. Frank H. Knowlton, of Washington, who, after a very careful 

 examination, reports concerning the rock that "it is reasonably certain 



3 Bull. Geol. Soc. Amer., vol. 13, p. 82, Amer. .Tour. Sci., vol. xiii, February, 1902, p. 

 184. 



