Waring: Geology of Northeastern Brazil. 193 



as is less evidenced at Curema, were structurally a sharp anticline. 

 In the canyon of the Rio de Piranhas, forty-five kilometers farther 

 west, the quartzite is also well exposed, and, as in the other places, 

 the range seems to be anticlinal. South of the range at Rio de 

 Piranhas, however, the gneiss seems to dip steeply north, instead of to 

 the south, as it should to conform to this structure; though a sharp 

 syncline at the south base of the serra may account for this seeminp 

 discrepancy. 



From Curema northwestward past Sao Jose da Lagoa Tapada and 

 across the small Serrinha Cascavel the gneiss has conetant west strike 

 and steep north dip, and is cut by the usual quartz and pegmatite 

 stringers. On the slope down nearly to Rio de Piranhas gneiss is 

 exposed, dipping eighty degrees to the north; but sandstone, which 

 occupies a considerable area in the basin of this river in the vicinity 

 of Sao Joao and Souza, appears in a low cliff on the north side of the 

 channel, and continues across the valley to the base of Serrinha 

 Macaco, three kilometers north of Souza. Gravelly sandstone is 

 there exposed at the edge of the valley, with hard, firmly cemented 

 conglomerate a few meters higher up the slope, together with rock 

 which resembles a feldspar porphyry, but may be a phase of the con- 

 glomerate. The higher slopes are of gneiss with some granitic phases. 

 At Sao Gongalo, at the border of the valley southwest of Souza. gneiss 

 is exposed dipping steepl}' to the north. Large boulders of gneiss 

 form a dam site on a small stream three kilometers to the south. 

 Near Nazareth there are several prominent peaks of gneiss, of which 

 Pico, capped by a perched boulder, is the most striking. Thence 

 southward to Serra Santa Catharina only gneiss was observed. South 

 of the range gneiss containing garnets is exposed at the river side at 

 Sao Jose. Thence toward Cajazeiras the gneiss has nearly vertical 

 north dip. In a few places questionable south dips may show some 

 overtu-ning or sharp folding. At Cajazeiras the gneise is well exposed, 

 with steep north dip, in the spillway of the town reservoir. About 

 twelve kilometers to the northeast, or one and one-half kilometers 

 south of, and seventy meters above, the lowland of Rio do Peixe, 

 there is a light-colored feldspathic rock, considerably kaolinized. 

 It is possibly a phase of the basal conglomerate seen a few kilometers 

 north of Souza; for at the border of the valley, the dark- red sandstone 

 appears fifteen meters above the lowland, making sharp contact with 

 the gneiss and dipping northeastward at an angle of thirty degrees. 



ANN. CAR. MUS , XIII, I4, Dec. 9, 192O. 



