woodworth: geological expedition to brazil and chile. 69 



the marine fossiliferous zone. In this loeahty the shales also carry 

 boulders and stones. That in the view being a boulder of gneiss 

 about twenty inches in the diameter on the exposed section. Below 

 the middle of the part of the bed shown in the plate there is a thin, 

 well-defined layer one and a half inches thick of the yellow material 

 which is called tillite in this paper. The layer consists of sand grains 

 and earth particles with coarse angular grains ranging to the size of 

 very small pebbles, and by its mode of occurrence is strongly sug- 

 gestive of deposition, like that of the stones included in the shales, 

 by floating ice, probably the manner in which the thicker beds of the 

 same character were laid down in this section. The shales part with 

 a thin splintery fracture subparallel to the bedding. 



The overlying tillite bed is composed mainly of fine earthy material 

 with coarse sand grains, and scattered pebbles; some of these latter 

 display glacial striae. Among the types of rock was noticed one 

 example of a coarse-grained diabase. This bed is about eight feet 

 (2.5 meters) thick, and is remarkable for the almost perfect develop- 

 ment of the bale structure so characteristic of some varieties of 

 igneous rock. No trace of stratification was detected within the 

 limits of the stratum. 



About two Brazilian leagues from Rio Xegro and further to the 

 south and east along this same road, the Ribeira das Rutes, a small 

 tributary of the south bank of the Rio Xegro, has cut a gorge with a 

 fall at its head in the blue unweathered tillite. This rock contains 

 rather abundant stones in a matrix of clay beset with small subangular 

 fragments of rock and coarse sand grains. 



North of the fossil locality above mentioned and lower down along 

 the course of the Rio da Vida Nova the ri\er road intersects a water- 

 worn conglomerate from six inches to two feet thick with pebbles of 

 sandstone and rocks resembling the formation in which it is inter- 

 calated. It is overlain and underlain by sandstones of the same 

 yellowish hue as the tillite beds, resembling a solidified loess. 



Seciiou from Rio Xrgro Southward to the Top of the Series. — South of 

 Rio Negro and upward in the series, sandstones and shales are crossed 

 by the Lages road as far as the Rio Lauren^o, at 1,500 mule paces 

 north of which I saw a large granite block four feet long lying on the 

 outcrop of bluish shales. On the south bank of the Rio Lauren9o a 

 thick sandstone formation comes in. Scattered pebbles and a few 

 boulders are seen along the same road farther south towards Sepultura. 

 Beyond this point southward and higher in the section no good 

 evidence of embedded pebbles was seen. 



