WOODWORTH: GEOLOGICAL EXPEDITION TO BRAZIL AND CHILE. 73 
indicate, by the detailed structure of the surfaces, that the down- 
throw was on the northeast side in accordance with the structure of 
the Orleans basin. It is evident therefore that repetitive small faults 
occasion the base of the Permian section in this district. 
The conglomerates are exposed along the river banks below the 
AAA AZ ” AG 7 a7 
| a eae Aw 
Ai AIT, 7 
SPR se 7 ES RR Bey 
ra 
Fra. 21.— Section of beds in Orleans basin, south bank of the Rio Tuberao. 
The rock on west is a broad trap dike. 
town and are best shown on the north bank under the railroad track, 
(Fig. 22). There is here a water laid conglomerate mainly of granite 
pebbles with a few quartzite and quartz pebbles. The conglomerate 
is overlain by cross-bedded grits, the cross-bedding dipping to the 
north and northwest as if deposited by currents of water flowing at 
least locally in that direction. The pebbles in the conglomerate bed, 
mostly three inches in diameter, sometimes attain five inches, and are 
embedded in a paste of granitic detritus. The subrounded shape of 
the pebbles indicates no distant journey and their lithological character 
betokens a derivation from the granitic terrane which immediately 
underlies the local Permian section. (See Plate 25.) 
Another exposure of the conglomerate about 90 meters down stream 
from the preceding exposure presents the cross-section of a north- 
south ridge of coarse pebbles 
enveloped in cross-bedded 
sandstones. In a layer of 
conglomerate varying from 0 
to 60 cm. in thickness the 
cobbles attain a diameter of Fic. 22.— Esker-like ridge of conglomerate 
9 S oe : in lower Permian beds; near Orleans, Sta. 
20 cm. The ridge-like de Sita faia en 
posit, so suggestive of a 
buried esker, is apparently continued across the river on the south 
bank of which there is a ridge-like exposure of conglomerate also 
covered by sandstones. A few yards east of the ridge on the 
north bank there is exposed a bed with rounded granite pebbles 
scattered through a sandstone matrix as if dropped by floating ice. 
