RIVER-DEPOSIT OF THE AMAZON. 769 
The top portion is grey, mottled with red specks, resting on beds of 
grey, white, and bluish-grey clay, which are in thick beds in parts, 
or in thin false-bedded layers in others. In one place they contained 
a sort of peat, mixed with brown clay and pieces of carbonized wood. 
Thomar cliffs show 
15 feet of red loam. 
15 ,,. yellowish false-bedded sand. 
These sections are all above the flood-level, as the river was full at 
the time they were taken. 
Turning now to the southern tributaries, we find that this deposit 
is not represented upon the Tapajos, the red and yellow cliffs border- 
ing that river belonging to the sandstone formation before mentioned. 
The face of the high land above Aramanahy is sloping and tree- 
covered, and does not afford a section showing its composition ; but 
it evidently belongs to the sandstone deposit, especially in the greater 
part of its lower portion. ‘The upper part may, however, be com- 
posed of a deposit made by the Amazon when it ran at a higher 
level. In fact, the upper part of the tableland at Parentins, Juruty 
Faro, &e. may be an old river-terrace. 
I here introduce a section occurring at Porto do Aleagre (fig. 3), 
in order to show the structure of a part of the underlying strata just 
spoken of, as well as adeposit which I take to be a more ancient river- 
terrace than the one under discussion. The terrace portion is made 
up entirely of reddish, yellow, and red-mottled false-bedded sand, 
capped by red loam, the whole having a thickness of 147 feet. 
Fig. 3.—Section at Porto do Aleagre. 
A. Old river-terrace. B. Sandstone. 
3 feet red loam. 
. 144 ,, false-bedded red, yellow, and mottled sand. 
5 ,, coarse, waterworn gravel bed. 
] 
2 
3. 
4, 2%,, grey clay. 
5. 
6 
it 
5 ,, purplish and grey irregularly bedded sandstone, cemented by 
white clay. 
23.,, mottled red and white clay. 
. 24 ,, friable sandstone. 
8. 30 ,, angular and partially rounded grains of yellowish sand, 
cemented by yellow clay into a friable sandstone. 
9 4 ,, hard, whitish, pebble sandstone. 
