Gênese de formações superficiais arenosas e evolução do relevo em tabuleiros costeiros do Litoral Norte do estado da Bahia

Abstract

The Coastal Tablelands (Tabuleiros Costeiros) of the Northern Coast of Bahia State are predominantly covered by sandy surface formations, including pedological layers developed over sandy deposits and soils that underwent podzolization. These surfaces are characterized by fragile soils, highly vulnerable to degradation, which has been intensified by real estate speculation linked to tourism in the region. This fragility reflects a geomorphological dynamic marked by processes of dissection, erosion, and deposition of sandy materials. Research conducted in the Coastal Tablelands indicates that the formation of sandy and podzolized soils, with low fertility and high susceptibility to erosion, such as Spodosols, occurs due to the transformation of lateritic soils through podzolization. However, in some areas, podzolization may have occurred in allochthonous sandy surface formations, such as aeolian and fluvial deposits. Moreover, the dissection of the Coastal Tablelands has contributed to the erosion of sandy and podzolized surfaces, exposing layers of the Barreiras Formation, which give rise to equally fragile soils, such as Cambisols. In this context, this research aimed to analyze the genesis of sandy and podzolized soils and to understand the landscape evolution in a dissected Coastal Tableland area in the Northern Coast of Bahia. Through the analysis of morphological, physical, chemical, mineralogical, morphometric, and morphoscopic data from samples described and collected in different geoenvironmental units and along a toposequence, an evolutionary model of the landscape was proposed. This model suggests a transformation system from Quartzipsamment-Spodosol-Cambisol, influenced by the presence of a duricrust, which is one of the cemented facies of the Barreiras Formation. Pedogenetic processes were triggered by the formation of concave areas at fault intersections, which favored the convergence of flows and podzolization. This process enabled the formation of Spodosols, facilitated by sandy sediments deposited by past fluvial dynamics over the duricrust. Subsequently, the incision of these depressions and the formation of drainage channels allowed the development of the slope under study and the exposure of a second facies of the Barreiras Formation in the downstream compartment, leading to the formation of a Cambisol. Therefore, the studies demonstrated the importance of these areas for understanding the podzolization process and the formation of sandy surface formations in humid tropical landscapes.