WOODWORTH: GEOLOGICAL EXPEDITION TO BRAZIL AND CHILE. 69 
the marine fossiliferous zone. In this locality 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 Negro 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 Negro, 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 river 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. 
Section from Rio Negro 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 Laurengo, 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 Laurenco 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. 
