400 THE CRETACEOUS AND TERTIARY GEOLOGT 



in still deeper and quieter water than any of the lower ones, are more homogeneous, 

 and contain the remains of fishes and a few cephalopods. No shallow water animal's 

 remains have thus far been found in them. Then followed the j^ressure that folded 

 broke, and in places, iiaitially metamorphosed, the cretaceous beds. This ended the 

 dejjression of the ocean's bottom. 



Pressitre. — The cretaceous beds of the Sergipe-Alagoas basin have been sub- 

 jected to more or less pressure, though this pressui'e has not been uniform. 



The following are the evidences of such pressure : 



1. Many of the fossils collected in this region are more or less crushed or other- 

 wise distorted. 



2. The beds as seen near Maroim, at the Lastro, and at other places along the 

 Maroim arm of the Tiio Sei-gipe, and especially along its western bank, are thi-own 

 into folds. 



3. Slaty cleavage is noticeable in the Ilha do Chaves, a mile below Propria. 



4. Superinduced cleavage and joint structure are seen in the sandstones of the 

 Serra d'ltabaiana and in those of the Serra de Maraba.* 



In some localities the limestones are metamorphosed, and their fossils completely 

 obliterated, while in many other places the obliteration of the fossils is but partial. 



The folds in these rocks indicate that the pressure by which the region was dis- 

 turbed came from the south-east. Although this pressure was sufficient to flex the 

 cretaceous beds, and, in places, to metamoi'phose them more or less, there is nothing 

 to show that it was great. The flexures are usually gentle and the rocks seldom dip 

 at a high angle, as will be seen from the accompanying table of dips. 



ECONOMIC. 



It is not to be wondered at that the popular notion that precious metals must 

 occur in all mountainous regions, has led to the supposition that the serras of Itabai- 

 aiia and Maraba arc auriferous. These mountains have been examined repeatedly in 

 the search for gold, silver and what not, but without success. As long ago as the 

 seventeenth century they were explored and found barren of such riches.f At the 



* Certain oUier saadstones of tliis region are partially metamorphosed. In some places this metamorphism is com- 

 plete, while in others it is but slight. Tlicre seems to be some doubt as to the exact place of these metamorphosed 

 siindstone beds in the scries, but the weight of testimony seems to sliow that they are tertiary. The metamorphism of 

 lliL'se particular beds cannot, I think, be adduced in support of the tlieory of pressure, for it is entirely due to 

 weathering. 



f "Within the jurisdiction of this captainship ('Sergipe del Rey') is the mountain of Tabayana ; from whence 

 several valuable ores were presented to the council of 19 ; but, upon proof, were found not worth farther looking 

 after." 1<)41. Voyages and Travels into Brazil by John Nieuliotl". Pinkerton's Voyages, Vol. XIV, p. 706. 



