Gomes, Moab PraxedesSilva, Luzia Liniane do Nascimento2021-08-182021-08-182021-05-07SILVA, Luzia Liniane do Nascimento. Registros holocênicos de sedimentação mista carbonática-siliciclástica na plataforma continental externa do Rio Grande do Norte. 2021. 133f. Tese (Doutorado em Geodinâmica e Geofísica) - Centro de Ciências Exatas e da Terra, Universidade Federal do Rio Grande do Norte, Natal, 2021.https://repositorio.ufrn.br/handle/123456789/33213The continental shelf of northeastern Brazil is characterized by a semiarid climate, warm temperatures, clear water, low sediment input, and mixed, carbonate-siliciclastic sedimentation. In this study, statistical analysis, mean grain size, sorting, skewness, and kurtosis were applied in 123 superficial sedimentary samples from the outer shelf of Rio Grande do Norte (RN) to verify the controlling factors of the distribution of sediments. In addition, geochemical analyzes were performed using the methods of X-ray diffraction (XRD) on 18 samples, X-ray fluorescence (FRX) on 20 samples, scanning electron microscopy, and energy dispersive spectroscopy on 10 samples (SEM/EDX), and 14C dating of six samples. Another technique used was digital image processing applied to Landsat 8/OLI satellite images in order to assess the spatial distribution of submerged features on the Brazilian continental shelf between the states of Amazonas and Bahia. The main results of this study showed that the statistical parameters, skewness, and kurtosis, were the ones that most evidenced the distinction between the siliciclastic and carbonate sediments of the outer shelf, indicating the terrigenous material as hydrodynamically incompatible with current conditions. The chemical compositions differed between the siliciclastic facies, composed of Si, Al, Fe, K, Zr, and Ti, and the bioclastic facies, constituted by the elements Ca, Sr and Mg. As for digital mapping, reefs occur in waters from 10 to 50 m deep, paleochannels showed a maximum extension of 35 km, occurring at depths of up to 80 m, and underwater dunes appear at depths from 10 to 100 m. Therefore, the integration of these data showed that carbonate sediments are from in situ and Holocene production, while siliciclastic sediments are relict and derived from continental rocks. The occurrence of reefs, paleovalleys and dunes indicate similar and favorable conditions for the establishment of these features during the Holocene along the Brazilian continental shelf.Acesso AbertoSedimentos siliciclásticosCarbonatoEstatísticaGeoquímicaFeições geomorfológicasdoctoralThesis