Identificação das áreas preferenciais de deposição de sedimentos quaternários nos maciços de Água Branca e Mata Grande – AL: uma contribuição para estudos paleoambientais

Abstract

The Quaternary is the period marked by great climatic oscillations that altered the moldogenesis and pedogenesis processes in different environments, whose records of these processes are kept in sedimentary deposits. These records are found in the massifs of Água Branca and Mata Grande-AL and their surroundings, which, due to orographic influence, favor areas of exception called brejo de altitude. In these spaces, slope deposits (colluvium) can be found, which are used as a data source for paleoenvironmental reconstruction. Thus, aiming to help future paleoenvironmental studies, the main objective of the research was based on mapping the depositional loci circumscribed in the Água Branca and Mata Grande-AL massifs, with the help of geotechnologies. Thus, in step 1 of the mapping, the flow directions were extracted and the loci demarcated using the surfer software (14). In step 2, a shapefile of these preferred deposition points was created. Step 3 was carried out in the Qgis 3.6 softwares, where a MDT was created for each massif using a raster image (STRM) of 12.5 meters, later the preferred points were added along with the drainage network. As a result of the data crossing, the sediment accommodation areas lodged between 300 and 600 meters of altitude were verified, in the recesses and areas of concave morphology. It was also noticed a significant amount of loci being cut by the drainage, leading to consider that the river channels play a relevant role in the drag and concentration of sediments in specific places of the massifs. These data allow the researcher to know in advance possible spaces for sediment accommodation, as well as the areas with better access and with greater probability of containing records, allowing for a lower cost of time in the process and efficiency in the research.