202 Annals of the Carnegie Museum. 



rock near the railroad is a coarsely granular gneiss, but there are low 

 granitic domes a short distance away. At Senador Pompeu the 

 gneiss strikes S. io° W., with vertical dip, but there seems to be con- 

 siderable variation in the direction of strike for several kilometers 

 north of this city. Southward also, the gneiss seems to be somewhat 

 crumpled, and to be sharply folded; but near Lages the strike becomes 

 more uniformly to the southwest, and thence to Iguatu swings gradu- 

 ally to the west, but with some sharp folding. 



The rock changes in character, as well as in strike and dip, south- 

 ward from Senador Pompeu. At this city it is much crushed, wdth 

 quartz, mica, and hornblende segregations. Southward the rock is 

 fresher and less crushed, with massive granitic material halfway to 

 Girao; but at this station decomposed gneiss is again prominent and 

 continues up across a low divide, down to Miguel Calmon, and south- 

 ward to the valley lands near Iguatu. The valley near Iguatu is in 

 part occupied by red sandstone, which is considered by Small-^ to be a 

 shallow synclinal remnant of the Cretaceous series. Near the base of a 

 low gneiss hill fifteen kilometers southwest of Iguatu the sandstone 

 dips gently northeast. The gneiss dips steeply to the north. Thence 

 westward to Sao Matheus the gneiss has a constant strike a little 

 south of west; and schist five kilometers east of Sao Matheus exhibits 

 the same strike, with vertical dip. 



West of Natal. On the railroad which runs westward, inland from 

 Natal, the western margin of the coastal sedimentary rocks is reached 

 about halfway between Ceara-Mirim and Taipu. This railroad was 

 not traversed by the writer beyond the former station, but the fol- 

 lowing note on the character of the crystalline rocks exposed along 

 this railroad is given by Jenkins: ^^ 



"In all the railway cuts it was noticed that dikes of granites and 

 pegmatites cut through micaceous schists. These dikes vary in 

 width from one to thirty meters, sometimes following the plane of 

 schistosity and sometimes cutting across it. Often one dike inter- 

 sects another. These dikes and schists do not show in the topography; 

 all are eroded and decomposed to the same surface level." 



From Natal to Recife. Along the railroad southward from Natal the 



2' Publ. No. 25 of the Inspectoria, p. 57, PL I. 



22 Geology of the Region about Natal, Rio Grande do Norte, Brazil, by Olaf Pitt 

 Jenkins. Proc. Am. Phil. Soc., Sept.-Oct., 1913, p. 12; Stanford Expedition to 

 Brazil in iqii. Vol. I, pp. 55-107. 



