branner: the stone reefs of brazil. 



21 



to 15*^ N. 45° ^y. beneath the hill. It overlies the strongly bedded 

 conglomerates and sandstones exposed on the right. The dip is not 

 constant, however, for one hundred and fifty metres down the shore the 

 dip is more nearly west. The exposure of the bituminous shales shows 

 them to be nearly two metres thick, but it is possible that they have a 

 thickness of three or four metres. 



Now the lower or left (south) end of this shale is a fossiliferous peaty 

 or bituminous bed with limy streaks and patches in it, while the upper 

 or right end merges into a mass of mushy nondescript purple and brown 

 sandy clays. Further, the discoloration has progressed more rapidly in 

 the sandstones beneath the shales than in the shales, so that the former 

 are already mottled and stained to a depth of six metres or more below 



Fig. 3. Exposure on the beach at Barreira do Boqueirao. 



the base of the shales. It should be added that the conglomerates of 

 this section contain water-worn granite boulders as large as a man's 

 head. 



At the City of Maragogy, State of Alagoas, only fourteen kilometres 

 north of the Barreira do Boqueirao, a section is exposed at the base of 

 the hill in the rear of the church. Here the bottom stratum, perhaps 

 not more than five or six metres above tide, is false bedded and mot- 

 tled so that it strongly resembles the bottom bed at the Barreira do 

 Boqueirao. 



At Riacho Doce {S. lat. 9° 36'), the shales and sandstones are exposed 

 from the mouth of the stream southward nearly to Gar^a Torta. As in 

 many other places, they are cut off" by the waves so that they are well 

 exposed only at low tide. They are much bent and faulted at this 



