BRANNER: THE STONE REEFS OF BRAZIL. 81 
the southeast corner rises to a height of twenty-one metres. On the 
western side of the island 18 a small bay, south of which is a quarry 
in the igneous rocks. Next to the quarry there are remnants of a 
calcareous fringing reef upon the beach, extending from that point to 
the southeastern point of the island. Along the shore of the little bay 
on the south side of the island is a piece of consolidated beach or stone 
reef. The rock is made of bits of shells, corals, sands, ete., exactly like 
the unconsolidated sands of the present beach. It is not hard and solid 
like the reef rock of Rio Formoso, but is soft and porous. 
This reef is between one hundred and fifty and two hundred metres 
in length, is from four to five metres wide at the widest, and is so high 
in places that only the very highest tides wet it entirely. On the land 
side it is buried beneath the beach sands, but toward the sea it is abrupt 
in places. It seems to be wearing away rapidly. 
The sandstone reef of Rio Formoso.’— Rio Formoso is an estuary in 
the State of Pernambuco, sixty kilometres southwest of the city of 
Pernambuco, and thirty-four kilometres southwest of Cabo Santo Agos- 
tinho. An isolated Tertiary hill stands back from the coast west of 
Gamella, and another stands just north of Rio Formoso, Against these 
hills lies a plain of later geologic age, that rises about eight or nine 
metres at most above high tide-level. Northwest of these hills, and 
north of the estuary, is a broad, low, flat country partly covered by loose 
sand and growing orchards of caju trees and other caatinga plants, and 
partly also by extensive mangrove swamps. Beyond (west of) this flat 
valley rise the low, approximately flat-topped table-lands of the interior, 
— in this vicinity composed of granites, gneisses, and crystalline schists. 
The structure and character of the Tertiary hills is shown where the 
tides of Rio Formoso have cut away the foot of the hill upon which 
stands the Church of Nossa Senhora da Guadalupe. The rocks are soft, 
white and gray sandstones, and red and yellow mottled el 
gently seaward. 
The rocks that lie against these Tertiary hills 
ays dipping 
are well exposed all 
nesian porphyries (p. 260). 
microscopic examination by th 
by myself, 
(The Cretaceous 
My determination of this rock was made after 
a 
e late Dr. George Н. William from material g 
athered 
and Tertiary geology of the Sergipe-Alagõas basin of Brazil. 
foot-note.) 
; M. Liais Speaks of Tertiary 
he refers to are these recent sandstones, 
ormoso reef has been published in P 
graphico Pernambucano at P 
By J. C. Branner, Trans. Amer. Phil. Soc,, 1889, XVI, p. 404, 
In his Climats Geologie, etc., du Brésil (р. 252) 
sediments on the island. The beds 
1 This description of the Rio Е 
by the Instituto Archeologico e Geo 
VOL. XLIV. 
ortuguese 
ernambuco, Brazil. 
