I9I3.] REGION ABOUT NATAL, BRAZIL. 405 



Summary. 



There are three principal series of rocks in the region about 

 Natal: the particolored sandstones and clays, exposed as sea-cliffs; 

 the underlying fossiliferous beds of limestone; and the crystalline 

 rocks in which are schists, gneisses, quartzites, shales, granites, etc. 

 The sedimentaries form a belt along the coast about thirty kilo- 

 meters wide, while the crystalline rocks make up the interior country. 

 Besides these formations the alluvial deposits in the valleys and the 

 wind blown sands of the coast are important features of the geology 

 of this region. 



The most important results from this work are as follows : 



1. The determination of an unconformity between the parti- 

 colored sandstone and clay series and the underlying limestones. 



2. The finding of fossils in the limestones. 



3. The determination that the limestones were laid down as 

 estuarine deposits, thus indicating a sunken coast at that time such 

 as exists now. 



4. The proof that the coast has sunken recently, and the com- 

 mercial effect that this condition has had upon the country in afford- 

 ing fine harbors, and in making good agricultural land by the deposi- 

 tion of silt in the rivers forming fertile valleys. 



5. The effect wind blown sand has upon the country in damming 

 streams and thus forming fresh-water lakes. 



6. The large supply of good water in the region of the sedimen- 

 taries in comparison to the lack of water in the dry interior. 



Leland Stanford University, 

 California. 



