216 DIAMOND AND CARBONADO WASHINGS IN BRAZIL. 



last-named point to the mouth of the river, with a width of only a 

 few kilometers. 



The first region is composed essentially of heavy beds of hard yel- 

 lowish sandstone which often pass into a conglomerate. These beds, 

 of which the thickness is estimated at more than 500 meters, are pro- 

 foundly disturbed, being thrown into folds that may be compared to 

 the waves of the sea, and are 'also cut by faults with the uplift sides 

 forming enormous steep-faced cliffs. It is therefore essentially a 

 mountainous region of the Appalachian type. 



The general elevation of the region is about 1,000 meters; some 

 peaks and ranges rise from 200 to 500 meters above this level, while 

 the deeper valleys are cut some TOO meters below it. 



On account of the hardness of the rocks and of the disturbances 

 (folds and faults) they have undergone the toj^ography is extremely 

 rough and the vegetation sparse, many of the ranges being almost 

 bare of soil and consequently of plant life. Here and there are small 

 areas of gentler topographic outlines where the decomposition of the 

 rocks has furnished a thick soil, and these places are generally cov- 

 ered with a scrubby A^egetation or with forests. On account of the 

 sandy nature of the underlying rocks the soil of the region is gener- 

 ally^ weak and is better adapted to cattle grazing than to agriculture. 

 As for mineral resources, the only ones thus far utilized are diamonds 

 and carbonados, and the geologic structure affords but little hope of 

 the existence of other minerals, except perhaps where some older 

 series of rocks may happen to crop out. 



The second region is made up partly of beds of yellowish sandstone 

 rather similar in appearance to those of the first region, but for the 

 most part softer, more clayey, and containing interbedded strata of 

 limestone some tens of meters in thickness. 



The thickness of this series seems to be from 200 to 300 meters, and 

 the beds are approximately horizontal, though there have probably 

 been some vertical displacements by means of faults. 



On account of its geologic constitution the region is relatively flat 

 and has a general elevation of from 500 to 600 meters. It is cut, how- 

 ever, by the valleys of the Paraguassu and its tributary, the river 

 Una, which are some 200 and more meters below the general level. 



The decomposition of the rocks is much more pronounced in this 

 than in the first region, so that it is only on the steepest slopes that 

 the character of the underlying rocks can be seen. 



The limestone when concealed, as it generally is, often discloses its 

 presence by the flinty segregations which clutter the roadways at 

 places where they have been set free by the decomposition of the 

 inclosing rock. 



The soil cap over the region is generally quite thick, and supports 

 forests which at many places are dense. Where the limestone comes 



