378 THE ( ]lETACEOUS AND TEKTIARY GEOLO(;Y 



To the north of Estuucia uo exposures arc known until one approaches the Pedra 

 da Cajahjba Avbich forms a part of the Itabaiana range of mountains.* From this 

 part of the piovinec to the Rio Sao Francisco near Propria the mesozoic basin is 

 bordei-ed on the hindwards side by the eastward extension of this same range of 

 mountains. In tlie province of Ahigoas, the Serra de Maiaba forms the north-west 

 boundaiy, and by its ti-cnd leads one to suppose that this north-west margin contin- 

 ues for some distance in a line parallel to the coast. 



Just where this basin ends to the noith-east, and indeed whether it ends at all, 

 either within the borders of Alagoas, or of Pernambuco even, is not known. The 

 oreoloo-y along: the coast between Maceio and Rio Formozo has never been examined, 

 and it is possible that this basin comes to an end between these two points. The 

 writer feels warranted in the opinion — though it is only an opinion — that Porto Calvo 

 is in the Sergipe-Alagoas basin, and it is possible that its beds are exposed at Rio 

 Formozo. An examination of the relations of the arch.'can rocks and what was at the 

 time supposed to be the tertiary beds at and near the mouth of the Rio Formozo in 

 the province of Pei-nambuco, does not definitely settle the question as to whether or 

 not the cretaceous beds continue to the north of this point. The beds seen at Rio 

 Formozo lie unconformably against the crystalline rocks, but it is not clear whether 

 the beds supposed, at that time, to belong to the tertiary do really belong to that 

 period. They are, in general appearance, certainly unlike any tertiary beds seen else- 

 where in Brazil, being made up of alternate beds of conglomerate, cla}^, chalk and 

 chalk with flint nodules. 



If then the cretaceous beds are continued fiom Alagoas and extend to the north 

 of Rio Formozo, it is possible that they underlie the tertiary' about Cape Sto. Agos- 

 tinho, and are continued on the landward side of that cape, underlie Pernambuco, 

 crop out at Olinda, Maria Fariuha, Iguarassii, the island of Itamaricii, and may even 

 connect with the mesozoic beds exposed at Paiahyba do J^orte and further north. 



LOCAL DETAILS. 



The present discussion of the Sergipe-Alagoas basin must be based upon facts 

 gathered for the most pait in the vicinity of Maroim, the Serra d'ltabaiana, along the 

 Rio Sao Francisco and the Serra de Maruba. 



* The beds of lliis range whicli I have referred lo the paleozoic [irobuljly underlie the erelaceous beds of all this 

 part of the coast. In ii leiler to lue, iu answer to one making inquiry regarding the nature of the region traversed by 

 liim from Bahia lo Sergipe, 5Ir. Derby writes: " la the trip across Biiliia and Sergipe, I found a series of shales and 

 sandstones in the region between the Rio Real and Itabaiana which is most probably the same seen in the mountains. 

 So far as I could see, there is nothing belweeu thai and the gneiss." 



