branner: the stone reefs of brazil. 243 



At Marceneiro Point coral reefs are exposed on the beach at low tide 

 with the calcareous beach sands lapping over them. In the bank above 

 the beach are exposed the partly consolidated calcareous sandstones 

 shown in Fig. 58, p. 90. Pontes and corallines are the commonest forms 

 in the reef here. 



At the bottom of the embayment south of Marceneiro there are coral 

 reefs along almost all of the beach, and soft calcareous sandstone is 

 exposed in the 1 to 2.2 metres bank above it. These coral reefs rest 

 directly upon Tertiary shales. 



_ KT 



Fig. 98. Section showing the relations of the coral reef to the Tertiary at 

 Barra do Passo. 



There is a decided break in the coral reefs off the mouth of Rio Cama- 

 ragibe, and they appear to begin again only five kilometres south of that 

 stream. Thence southward to Ponta Verde north of Maceio the coral 

 reefs are more broken and fragmentary than they are to the north. 

 These fragmentary reefs were not examined except where they lie along 

 the beach. Some of the beach exposores are of more than usual inter- 

 est on account of their showing the relations of the coral reefs to the 

 stone reefs and to the eroded Tertiary strata of the land. 



South of Rio Santo Antonio Grande the coral reefs for two or three 

 kilometres are almost connected with the beach, — perhaps quite so at 

 the lowest tides. 



At the point 1.4 kilometres south of Rio Sapucahy there is a sandstone 

 reef overlying the coral I'eef. In view of the importance of this locality 

 in showing the geologic relations of the stone and coral reef, I repeat 

 here what has been given in the description of the Sapucali^ stone reef : 

 "Following the beach southward from the mouth of the Sapucahy 

 [a small river of the State of Alagoas about thirty kilometres northeast 

 of Maceio] it curves gradually seaward and then back landward again, 

 forming a sandy point, part of whicli is shown on the accompanying 

 map. At a distance of 1.4 kilometros from the mouth of the Sapucahy, 

 this sandy point laps over one of the coral reefs that here run parallel 

 with the coast. And just at this point on the beach begins another 



