190 Annals of the Carnegie Museum. 



meters thick, with a little crystalline limestone. The material strikes 

 west, with steep south dip. A hillside one-half kilometer farther 

 north is of cherty material, but schist and limestone appear again on 

 the north side of the ridge, which seems to be part of a sharp anticline. 

 Thence northward coarsely-banded gneiss appears, with nearly 

 vertical foliation planes striking west; but the rock shortly becomes 

 bouldery and granitic in character. 



On the slope descending northward to Rio Umary there is pegmatite 

 composed of vitreous quartz and pink feldspar, and quartz fragments 

 are scattered over the surface of the decomposed gneiss. An alluvial 

 area three kilometers wide borders the river in this locality, with 

 crumpled gneiss on low slopes at the north border of the lowland. 

 Between the Rios Umary and Apody the surface is covered with sand, 

 which seems to be composed of angular fragments derived from dis- 

 integrated granite; but soft red sandstone, belonging to the Cretaceous 

 series, is exposed along the north bank of Rio Apody, and the low 

 slopes near Apody are covered with sand which is probably derived 

 from this sandstone. For three or four kilometers northeast, down- 

 stream from Apody, the red sandstone continues; and thence down- 

 stream to Mossoro non-crystalline limestone, which overlies the 

 sandstone conformably, forms clifTs, which border the river and dip 

 gently coastward. Northwestward from Mossoro the surface rises 

 gently up the limestone tableland to Vertentes, then lowers slightly 

 to an escarpment, where the surface drops seventy meters to wide 

 lowlands along the Rio Jaguaribe. The rock exposed across the 

 tableland (Chapada do Apody), is wholly limestone, though it is 

 partially covered in a few places with a film of sandstone and iron- 

 cemented gravel, which is presumably a remnant of the coastal 

 Tertiary materials. The scarp where descended exposes only lime- 

 stone, but the underlying sandstone is in evidence in the river channel 

 and adjacent low slopes. 



At Passagem das Pedras on the Rio Jaguaribe at the upper limit of 

 the tide, gneiss strikes N. 20° W., magnetic, or about N. 35° W., true, 

 with dip of seventy degrees to the northeast. Between the river and 

 the village there is a prominent ledge of white quartz, or possibly 

 quartzite, for Serra Arare, situated two kilometers to the west, is 

 composed in part of quartzite, with dip and strike api)arently con- 

 formable with that of the gneiss in the river Conformable structure 

 is also shown in gneiss, carrying much quartz, at the base of the serra. 



