Estudo sedimentológico dos depósitos eólicos ativos do campo de dunas do Baixo São Francisco em Alagoas

Abstract

Dunes are forms created from the accumulation of sediments that develop morphologies from the stacking of sediments. Sedimentological analysis has been used to study coastal Quaternary sediments, to infer local dynamics and to differentiate grains of different ages. Therefore, the study aimed to characterize and analyze the sedimentology of the Piaçabuçu dune field, an area composed of active and inactive dunes, with different shapes and sizes, being a suitable environment to study from a sedimentological point of view, with a focus on in the active dunes. 15 samples were collected in December 2019, they were used for the development of this study. In the laboratory, the processes for granulometric analysis, washing, sieving and weighing of the samples took place, separating the grains present in them by their size. In sequence, Sysgran 3.0 and SedLog 3.1 software were used, where, based on statistical calculations, it will deliver the classification of sediments using the Shepard Diagram and the preparation of stratigraphic profiles, respectively. Using the aforementioned software, the following results were obtained. Asymmetry: approx. symmetrical (27%), positive (20%), very positive (7%), negative (40%) and very negative (6%); kurtosis: platykurtic (46%), mesokurtic (13%), very platykurtic (27%), very leptokurtic (7%) and extremely leptokurtic (7%); sedimentological distribution and average diameter, with greater presence of very fine sand and coarse silt; sphericity and grain bearing, spheroidal and sub-angular in all samples, suggesting that the sediments underwent a long process of transport and wind reworking. The granulometric analysis of the 15 samples showed the predominance of the sandy fraction throughout the sample area. The methodology sought to achieve the objectives proposed by the present study, being a challenge in the search to study the Coastal Geomorphology of the State of Alagoas, where the theme demands revisions and updates. The covid-19 pandemic was an impediment in the field and laboratory stages for the development of this study, as it limited the ability to produce more robust data on the studied area, however, the data obtained and processed, even initial, are promising.