J. C. Branner — The Tomhador J£scarpment. 341 



form the watershed hetween the Salitre drainage and the 

 drainage into Rio Itapicuru, and into Rio do Pogo Comprido. 

 Tlie geology of this watershed was examined by the writer at 

 two other points fnrther north, and the sections as there made 

 out will be of interest in connection with the one already 

 given. 



A trail crosses the range between fazenda da Pedra Branca 

 on the east and fazenda da Varzinha on the west side of the 

 watershed. At this place the range no longer forms a bold 

 escarpment ; indeed the Tombador sandstones and the rocks 

 that overlie them are all lacking, or are not exposed, up to the 

 Salitre limestones which rest directly or almost directly upon 

 the granites. 



It is of interest to note that granites with a few other crys- 

 talline rocks extend from the base of this ridge eastward past 

 fazenda Lagoa do Mato to the base of the Jacobina range, and 

 that in this granitic area there are here and there sharp quartz- 

 ite ridges with their beds standing nearly or quite on end. 

 The fazenda Pedra Branca takes its name from one of these 

 white quartzite hills. 



The following section shows the geology as it is exposed on 

 this trail. 



Fig. 5. 



■?c^ra,Bi-a.ii.t«, 



Fig. 5. Section showing the general geology between fazendas Pedra 

 Branca and Varzinha, a distance of 18 kilometers. 



The hill where the road passes over it is less than a hundred 

 meters high. The granites at the base continue half way up 

 the slope ; above them is a narrow zone of quartzites and 

 schists, and these are followed by decomposed cherts which 

 cap the ridge. Going down the gentle westwai'd slope of this 

 ridge the cherts are found to overlie and to be part of the 

 Salitre limestone series. The limestones are mostly compact 

 and dark blue. They here have some thin strata of yellowish 

 shale interbedded with them. These limestones mostly have 

 a gentle dip toward the west ; but as the mountains near Var- 

 zinha are approached the limestones are highly tilted in places. 



Five or six kilometers further north the trail from Campo 

 Formoso to Varzinha crosses this same watershed on fazenda 

 Campo Frio. This route furnishes another section from the 

 granite base of the Serra de Jacobina at Campo Formoso to 

 Varzinha, which is on and near the Salitre limestones. 



