t^^ 



STONF REEFS 



OF THE 



RIOS CUNHAHUAND SIBAUMA. 



RIOCUNHAHU 



ATLANTIC OCEAN 



Fig. 17. 



N^orth of the Cnuhahil there is only 

 a narrow flat strip of land, barely wide 

 enough for the houses of the village, 

 between the river and the Tertiary (1) 

 hills to the north. 



Where the reef north of the river 

 laps back upon the beach the Ter- 

 tiary (T) 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 (?) 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 (?) hills draw off to the 

 west and swing up the valley of the 

 Sibauma, and the belt of sand dunes 

 widens across the mouth of the Si- 

 baiima valley. 



Xorth of the Rio Sibauma the sand 

 dunes lie between the beach and the 

 Tertiary (J) 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 ck)se to and j^arallel 

 with the Tertiaiy 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 Cunhahii and Sibauma reefs — 

 originally one reef — have their south- 

 ern end on the beach 2,7 kilometres 

 south of the mouth of the Pio Cun- 

 hahu. 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 

 l)atchy one. The only other signs of 

 it are immediately south of the mouth 



