196 BRANNER 



motive and special car at my disposal on one trip from Maceio 

 to Assemblea, and had them stopped whenever the geology made 

 it desirable. 



As a rule the geology of the region of metamorphic and 

 crystalline rocks is complicated, and in notes made as these 

 were but little else can be done than to indicate the margin of 

 the area where the crystalline rocks are overlapped by the later 

 sedimentary beds. 



The Lagoa do Norte is of interest in connection with the 

 geography and later geology of the region. This lake, although 

 large, is so shallow that only very small boats can navigate it. 

 It has a depth of channel of only two or three meters along its 

 south side. The water is brackish, and the tides are but little 

 felt in the lake ; the rise and fall is only about 0.3 meter. 



This lake and Lagoa Manguaba, a similar body of water 

 eight kilometers southwest of it, were valleys carved in the 

 sediments of this region in Miocene Tertiary times, when the 

 continent stood at a higher level. After these valleys were ex- 

 cavated the region sank and the valleys were converted into 

 bays. These ba3^s, in the course of time, had their mouths 

 closed by the silts thrown back into them by the ocean, and still 

 later they silted up as we now find them. Newly made land 

 has already filled up the stream valle3^s emptying into these 

 basins, and the land is constantly encroaching upon the lakes. 

 They are rapidly silting up and must disappear soon, in the 

 geological sense. 



Plate X, made from a photograph, is a view looking south 

 across Lagoa do Norte from Fernao Velho, and showing the 

 Eocene (?) plateau and its steep oceanward escarpment south of 

 the town of Coqueiro Secco. 



The Maceio end of the railway is upon the low, flat, sandy 

 lands upon which stands the business portion of the cit}^ known 

 as Jaragua. Behind this low ground rises a line of flat-topped 

 hills — the margin of a plateau — of parti-colored sediments sup- 

 posed to be of Eocene Tertiary age. These hills follow the 

 coast northeast for hundreds of miles, broken here and there by 

 the valleys about the mouths of streams. From the lighthouse 

 on top of the hills at Maceio this sedimentary plain appears to 



