Geomorphology of Alagoas State

Alagoas lies in the southern or external sector of the Borborema Province. Its territory comprises Proterozoic lithologies with Archean and Paleoproterozoic nuclei bounded by Meso- and Neoproterozoic fold-belts. Phanerozoic sedimentary covers of the Tucano-Jatobá basins (Paleozoic) outcrop in the northwestern most sector of the State, along with other sedimentary units along the coastal strip, like the Cretaceous formations of the Alagoas marginal rift basin, the Neogene covers that overlie them, and Quaternary fluvio-marine plains. Since the early physiographical descriptions of its territory, the relief compartments of Alagoas have been arranged in four sets of landforms: the tablelands (tabuleiros), the crystalline highlands (Planalto da Borborema), the Peripheral Depression (situated between the two former units), and; the Sertanejo Pediplain (Pediplano Sertanejo). Beyond those, the residual landforms of Santana, Mata Grande, and Água Branca massifs, the fluvial and coastal plains, and the escarpments of the Borborema Highlands have also been identified as morphostructural sub-units. A new subdivision of the State’s macro-relief units was proposed based on the relationship between the macro-morphological compartments and the lithostructural units. Namely, the morphostructural landforms are the crystalline highlands, the sedimentary plateaus, the semi-arid depressions and associated residual massifs, and fluvial and coastal plains.