292 J. C. BRANXER OUTLIIsES OF THE GEOLOGY OF BRAZIL 



bard in his "Exploragao da parte snl do estado de Pernambuco/' and by 

 Dombre in his "Viagens." A strip in the west end of the state is shown 

 on SmalFs map of the geology of Pianhy, The fossils from Farinha are 

 dsecribed by Cope, Dall, C. A. AAThite, and Eathbun, and Miss Maury 

 contributes a valuable note on the correlations of the Maria Farinha beds. 



The island of Fernando de Noronha belongs to the State of Pernam- 

 buco ; the geology of that island is described by Branner, Darwin, Davis, 

 Lea, Eenaud, Eidley, Geo. H. Williams and Gill, and Costa. 



The stone reefs of the State of Pernambuco and the east coast are de- 

 scribed by Branner. 



General geology. — Eocks of Archean age cover most of the State of 

 Pernambuco. Along the coast is a belt of Tertiary sediments; north of 

 Olinda this belt is about forty kilometers wide, and in some places is 

 underlain with Cretaceous rocks ; south of Olinda this belt is only ten or 

 twelve kilometers wide and the rocks are probably all Tertiary. In the 

 extreme western end of the state the mountains along the Piauhy and 

 Ceara frontiers are capped by Cretaceous rocks containing fossil fishes. 

 At several places through the interior old Paleozoic remnants are faulted 

 or folded into the Archean. For lack of data these infaulted areas have 

 not been outlined; one of them is in the Serra Eussa between Victoria 

 and Gravata. A similar area is west of Canhotinho. The outliers of 

 sedimentary rocks between Jatoba and Buique and near Aguas Bellas 

 have thus far yielded no fossils, and the age or ages of those beds is not 

 definitely known. They are referred provisionally to the Upper Permian 

 because they are stratigraphically in the place occupied by the Permian 

 beds at Aracy, Bahia. Lombard supposed the beds at Buique were pre- 

 Cambrian, but there is no evidence in support of such a theory (Lom- 

 bard, "Eelatorio apresentado," page 131. Eecife, 1895). Trachytes are 

 exposed on the coast just north of Cape Santo Agostinho, and the island 

 of Santo Aleixo is of rhyolite. The island of Fernando de Noronha is 

 mostly phonolite, but there are some small areas covered by sandstones 

 formed by the hardening of sand-dunes. 



The stone reefs characteristic of the Brazilian coast from Ceara to 

 Bahia, inclusive, are well developed at several places on the coast of Per- 

 nambuco, notably at Eio Formoso, Eecife, and just south of Cape Santo 

 Agostinho. Several Brazilian seaports are formed by stone reefs, namely, 

 those of Pernambuco, Natal, Porto Seguro, and many of minor impor- 

 tance. These reefs are old sand beaches through which water from the 

 land has filtered, consolidating the sand by the precipitation of lime be- 

 tween the sand grains. They vary greatly in length and breadth; the 

 one at Pernambuco is from 20 to 60 meters wide. Their surfaces never 

 rise above high-tide level. 



