RIO SIBAUMA. 
STONE REEF S 
OF THE 2 
RIOS GUNHAHU AND SIBAUMA, |; 
ce GILMAN 
MILES 1 
A pia 
wur © у ч 
RIO CUNHAHU 
[mal 
North of the Cunhahú there is only 
a narrow flat strip of land, barely wide 
enough for the houses of the village, 
between the river and the Tertiary (7) 
hills to the north. 
Where the reef north of the river 
laps back upon the beach the Ter- 
tiary (1) hills are from one hundred and 
fifty to two hundred and fifty metres 
west of it; and this is as near as the 
reefs and the Tertiary (1) sediments ap- 
pear to approach each other. North of 
this point the reef lies along the beach 
all the way to its northern end, while 
the Tertiary (1) hills draw off to the 
west and swing up the valley of the 
Sibaúma, and the belt of sand dunes 
widens across the mouth of the Si- 
baúma valley. 
North of the Rio Sibatima the sand 
dunes lie between the beach and the 
Tertiary (1) bluffs for half a kilometre, 
but here the colored beds are exposed 
on the beach, and the highest tides 
come within three metres of the base 
of the bluff, From this point north- 
ward the beach is close to and parallel 
with the Tertiary bluffs which continue 
to and beyond Moleque Point and Ponta 
do Pipa. These hills average about 
twenty metres high along their faces 
near the shore; inland they are higher. 
The Cunhabú and Sibaúma reefs — 
originally one reef — have their south- 
ern end on the beach 2.7 kilometres 
south of the mouth of the Rio Cun- 
hahú. This southernmost section is the 
inner reef of the two, and has a total 
length of eight hundred and seventy- 
five metres. It is nearly flat on top, 
but structurally it has a gentle sea- 
ward dip. The rock is rather soft, but 
otherwise it is like the ordinary reef 
rock. 
This inner reef is, however, only a 
patchy one. The only other signs of 
it are immediately south of the mouth 
