Waring: Geology of Northeastern Brazil. 191 



From this serra, red-brown quartz-schist is obtained for flagging in 

 Passagem das Pedras and Uniao. 



On crossing the valley of the Rio Jaguaribe and going northwestward 

 from Sao Bernardo das Russas, deep, sandy soil covers the surface 

 for several kilometers. Gneiss was seen in a reservoir eight kilometers 

 northwest of the town, but the sandy soil continues for about four 

 kilometers farther. Thence gneiss becomes more frequently exposed, 

 with constant northwest dip, as far as Santo Antonio. From this 

 place southward the rock is more granitic, with some bands of thick- 

 banded gneiss. In a reservoir at Jatoba the bed-rock is well exposed, 

 being granitic rather than gneissic in texture, yet exhibiting a wavy 

 structure traversed by numerous veinlets. Four kilometers to the 

 south pink granitic gneiss strikes north with vertical dip, and three 

 kilometers farther south gneiss with steep southeast dip is exposed. 

 The surface then becomes sandy, to the alluvial lowlands, about ten 

 kilometers wide, near Limoeiro. Southeast of this city several granitic 

 knolls rise ten to twenty meters above the level of the lowland; but 

 no crystalline rocks were seen along the escarpment of Chapada do 

 Apody, which borders the valley on the southeast. The limestone of 

 this tableland rises southward so that whereas southeast of Uniao 

 it forms the entire escarpment, at Curraes it forms a capping only five 

 meters thick upon the sandstone, which here composes the main part 

 of the scarp. Southward across the highland there are several wide 

 exposures of the bare limestone; but for the most part there is a thin 

 soil, given a brown tone by iron-oxide gravel. In a few places masses 

 of conglomerate, twenty or thirty centimeters in diameter, from 

 which the gravel apparently is derived, were seen. Four kilometers 

 north of Soledade the limestone for one hundred or two hundred 

 meters carries plentiful turritella-like fossils. On the scarp descending 

 to Apody the limestone is about twelve meters thick, being underlain 

 by dark-red and blue-gray sandstone. 



Southwest from Apody sand and sandstone cover the surface for 

 several kilometers, with coarse gravelly sandstone, seemingly basal 

 material, in evidence in a few places; but about ten kilometers from 

 Apody, granitic gneiss is exposed. The foliation planes there lie 

 nearly horizontally, but southward the dip rapidly steepens to a 

 nearly vertical south dip. To and beyond Angicos the gneiss is cut 

 by occasional veins of quartz and dikes of pegmatite. Near Angicos 

 the strike swings to a little south of west, with steep southward dip. 



