Branner : Geology of Alagoas, Brazil. 15 



considcral)I\- wrinklrd and somewhat faulted, liul the general struclure 

 shows that they dip westward beneath the bluffs. The shales exposed 

 on the beach and in pits in the palm groves near by are black, foliated, 

 and thin-bedded, and contain a good many remains of fishes, diatoms, 

 ostracods, and foraminifera. The cases cited above show that the sedi- 

 ments along the Alagoas coast north of Maceio have a general and decided 

 dip toward the land. 



Why the Coast Sediments Dip Landzvard. — Two explanations suggest 

 themselv -. for this apparently universal landward dip of these beds. The 

 arst one is that the beds were laid down in a basin parallel with the coast, 

 and somewhat similar to that found at and north of the city of Bahia, and 

 that the ocean has now cut away the entire seaward edge of that basin 

 leaving the westward dipping beds exposed. There is nothing impossible 

 or even improbable in this theory. When the sea shall have encroached 

 upon the coast at and north of Bahia a few kilometers further, it will have 

 cut aw'ay a narrow belt of crystalline rocks and will expose the landw'ard- 

 dipping shales of the Bahia basin. 



The fact that the granites are exposed at many places along the coast 

 of Alagoas beneath the shales, and the fact that the granite bottom of the 

 basin does not appear in the section made across this sedimentary belt 

 by the railway running from Maceio to Albuquerque lends support to 

 this theory. 



The other suggested explanation of the landward dip of the sediments 

 on the coast is that the removal of the 50 to 90 meters of sediments along 

 the coast has permitted the upbending of the rocks relieved of pressure 

 on the shore just as we have the upthrust of the floors of tunnels in deep 

 mines and similar phenomena along the bottoms of deep canyons cut 

 through thick sediments. In either case it seems that the sediments are 

 somewhat thinner on the immediate coast than they are a few kilometers 

 inland. 



Color of the Coastal Sediments. — It has already been stated that the 

 coastal sediments are highly colored. The most pronounced colors are 

 yellow, red, and orange; but almost all the colors of the rainbow may be 

 seen in the large exposures. Sometimes the colors are more or less banded 

 and one is led to infer that this banding follows certain horizontal beds. 

 Sometimes the beds are mottled rather than banded, and sometimes it 

 even happens that there is a vertical gray, whitish, or leaden-colored band 

 that cuts square across the usual horizontal beds. 



It was formerK- supposed that these high colors had some stratigraphic 



