GENERAL AXD ECONOMIC GEOLOGY 247 



the "Sant'Anna limestone" fossil fishes are found that show satisfactorily 

 the Cretaceous age of this series. 



The irregular zone of coastal sediments shown on the map as Pliocene 

 extends along the entire coast and varies in width from 5 to 35 kilome- 

 ters. The rocks are mostly soft reddish^ yellow, and mottled sandstones 

 and clays in which no fossils have yet been found in Ceara. The Tertiary 

 beds all dip gently toward the ocean. Some of the beds contain much 

 iron locally. They are assumed to be Pliocene because there is a lower 

 series at Mossoro known to be Eocene. The thickness of these sediments 

 varies greatly, but in the State of Ceara they probably do not exceed 50 

 meters. 



At a few places along the coast, notably at Canoa Quebrada, near Ara- 

 caty, are short sandstone reefs of Quaternary age, similar to those at 

 Natal and Pernambuco. 



Economic geology. — Gold has been washed at many places, but I know 

 of no gold mine now in operation in the state. Iron is abundant at many 

 places, both in the old crystalline series and in later deposits, but it is 

 not mined, and no systematic search has been made for ore bodies worth 

 working. Copper in the form of the carbonate is known at Fazenda 

 Pedra Yerde seven kilometers northeast of Yicosa. The deposit is de- 

 scribed in Small's report, at page 141. Bituminous shales are found in 

 the Cretaceous rocks of the Serra do Araripe. Books and articles on the 

 state give long lists of minerals found there, but it is not claimed that 

 they are sufficiently abundant to warrant exploitation. AA'hite crystalline 

 marble occurs at several places in the interior, and ordinary limestone 

 is abundant along the eastern flank of Serra Grande and in the Serra do 

 Araripe, in the southern end of the state. As the state suffers much 

 from long periodic drouths, subterranean water supply is of great impor- 

 tance in Ceara. Such water is found most certainly in the coastal sedi- 

 ments, though it is occasionally found in small quantities in the Archean 

 area. Data collected by Small show that out of sixty-one wells sunk in 

 the sedimentary beds along the coast 77 per cent yielded fairly good 

 water, while out of twenty-three wells sunk in granites, gneisses, or schists 

 45 per cent only yielded fairly good water (Small, page 56). 



Geologic Maps of Ceara 



Crandall and AYilliams. — In 1910 the "Inspectoria de Obras Contra as 

 Seccas" published a geologic map of the States of Ceara, Rio Grande do 

 Norte, and Parahyba. The authors of the map were Eoderic Crandall 

 and H. E. Williams, both, at that time, assistants on the Servico Geo- 

 logico e Mineralogico do Brasil. The map was on a scale of 1 to 3,000,000 



