Branner — Geologxj of the Serra do Mulato. 



261 



part of this scries of sediments. The bhiff, however, is more 

 than a hundred meters high, and, being inaccessible, could only 

 be ascended at one point on the east side, and no conglomerates 

 were seen at that place. Carefnl seai-ch was made for fossils, 

 bnt the materials are most unpromising. At a few places there 

 were found some dark angular fragments that suggested plant 

 remains, but if they are such, they are quite unrecognizable. 

 One thin (20 centimeters) bed was found which from its resem- 

 blance to a stratum of mud seemed to hold forth some promise. 

 It was so altered, however, that it was quite schistose. 



The age of these sedimentary beds cannot therefore be deter- 

 mined at present either from fossils found in them or by refer- 

 ence to any rocks immediately above or below them. 



The altitude of the top of the mountain above sea-level is 

 865 meters ; the thickness of the horizontal quartzite beds that 

 cap the summit is something more than 125 meters ; the height 

 of the mountain top above the old flood plain at its base is 465 

 meters. 



Fig. 5. 



--p-"-^' 



• '/ -^ ^^ 



/ / 



Fig. 5. Serra do Boqueirao and Serra da Cruz seen from the top of Serra 

 do Mulato. The flat summits are Tombador quartzites. 



From the top of the Serra one has a good view of the two 

 mountains that lie to the east. These are the Serra do Boque- 

 irao lying next to the Serra do Mulato, and the Serra da Cruz 

 still further to the east. Seen from here, the geologic structure 

 of these two mountains and their relations to the Serra do 

 Mulato are plain and simple. The horizontal quartzites that 

 cap the Serra do Mulato can be followed with the eye along 

 their outcrop to these neighboring mountains, which are capped 

 by this same series of sediments. The Serra do Boqueirao is 

 somewhat lower than the Serra do Mulato, of which it is simply 

 a spur. The valley that separates these two points is a low 

 breached anticline. The Serra do Boqueirao is a synclinal 

 ridge, while between this and the Serra da Cruz is another 

 anticlinal valley. The folds forming these valleys and ridges 

 are gently and clearly defined, and all three of these mountains 



