342 J. C. Bi'anner — The Tomhador Escarpment. 



The road from Cainpo Forinoso to Cainpo Frio is over 

 granite all the way except near the villag-e of Pogos, where 

 there is a little quartzite, and a few kilometers further west, 

 where there are some thin ])atches of basal conglomerate resting 

 directly on the granite. The crest of the watershed between 

 the Salitre drainage and the Itapicnrii. drainage is only a kilo- 

 meter or two west of the granite area. This crest is remark- 

 ably flat, the soil is of a deep red color, and the abundance of 

 loose flint fragments on both slopes suggest that the flint-bear- 

 ing beds form the crest of the divide. The topography of the 

 M'atershed and the appearance of the hills to the north and 

 west all suggest that the limestones with which the flints are 

 associated dip gently toward the Salitre valley. Exposures of 

 bedded limestones a few kilometers further west bear out this 

 idea. 



Attention should be called to the fact that although this 

 watershed does not form a bold bit of topography, it has an 

 altitude of 800 meters at the point where the trail crosses it, 

 while the Moi-ro da Mina, one of the prominent peaks of the 

 Serra de Jacobina, has an altitude of 950 metei's a. t. In other 

 words, this watershed is a high one in spite of its lack of bold- 

 ness, and it is the geographic prolongation of the Serra do 

 Tombador in spite of the absence of the Tombador series of 

 rocks. 



Further north this watershed swings westward and reaches 

 Kio Salitre at the falls of that stream some thirty-five kilo- 

 meters south of Joazeiro. The Tombador sandstones again 

 make their appearance somewhere north of the section given 

 above, and thickening up they begin to form the bold topog- 

 raphy just east of the cachoeira do Salitre. The falls them- 

 selves are made by passing over the Tombador sandstone 

 ledge. "West of Rio Salitre they rise into the broken moun- 

 tainous region and appear again capping the Serra da Ci'uz and 

 Serra do Mulato as explained in the preceding chapter.* 



The character and apparent structural relations of the Tom- 

 bador beds to those of the Jacobina range suggest that the 

 two ranges may be geologically identical, and that the valley 

 between may be simply a breached anticline. The possibility 

 of such relations was entertained in the early part of the field 

 work, and though it was soon abandoned, it has not been lost 

 sight of. In the total absence of fossils from the rocks of 

 both ranges one is obliged to depend entirely upon lithologic 

 and structural features to settle this question. The chief fact 

 in support of the theory of the identity of the two series is 

 that they both rest upon the old granitic series. 



*This Journal, Oct., 1910, pp. 256-263. 



