GENERAL AND ECONOMIC GEOLOGY ZOO 



A soft yellow sandstone that overlies the Triassic and forms the top of 

 the plateau of Grajahn is referred by Lisboa to the Cretaceous. In places 

 these sediments are argillaceous; the whole series dips gently toward the 

 coast. 



Along the coast of Maranhao is the Tertiary zone characteristic of the 

 coast of northern Brazil. These beds are horizontal sediments, here and 

 there cemented with iron. Where the sea is encroaching on them they 

 form bluffs, and where the sands are encroaching on the sea the coast is 

 low and the hard rocks are covered by sand-dnnes. 



It was formerly supposed that the marine fossils found at Pirabas, on 

 the coast of Para, were Cretaceous, and they were therefore included in 

 Dr. C. A. White's description of the Cretaceous fossils of Brazil. Later 

 studies have shown that those fossils are Eocene. ^^ Eeference is here 

 made to the Pirabas fossils because Dr. Lisboa found at Carutapera, in 

 the northwest corner of Maranhao, fossiliferous limestone '^Vith a fauna 

 similar to that of Pirabas.'^ The Carutapera region is therefore to be 

 classified as Eocene unless a fuller study of the fossils found there should 

 warrant a different conclusion. 



Economic geology. — But few minerals of economic importance are cer- , 

 tainly known in the State of Maranhao. Some gold has been mined; 

 bauxite is reported in the sedimentary beds of the west, and Dr. Lisboa 

 found bituminous shales near Codo and at several other places in the 

 state. Burlamaqui reports such shales on Eio Mearim near Barra do 

 Corda. Limestone, probably of Permian age, is abundant on Eio Grajahu, 

 where it has a thickness of 25 meters. Iron has long been reported from 

 the island of S. Luiz, but there is no information available regarding the 

 quantity and quality of the ore. 



Geologic Map of Maranhao 



Lisboa, 1914. — Dr. M. A. E. Lisboa published, in the American Jour- 

 nal of Science for May, 1914 (volume 187, pages 425-443), an article on 

 the Permian geology of northern Brazil, and accompanying it was a small 

 map showing the geology of a large part of the State of Maranhao. It is 

 on a scale of 1 to 1,126,760, and four geologic divisions are represented, 

 namely: crystalline, Permian, Triassic, and Cretaceous. 



Bibliograpluj of the Geology of Maranhao 



Anon : Mines d'or . . . pres de Saint Louis de Maranhao. Nouvelles Ann. 

 des Voyages, sixth series, volume II, pages 112-114. Paris, 1885. 



°- Carlotta Joaquina Maury : A contribution to the paleontology of Trinidad. Jour. 

 Acad. Nat. Sci. of Philadelphia, vol. xv, pp. 32-33. Philadelphia. 1912. 



