Sedimentação recente e palinologia do Talude Continental Superior Amazônico-Maranhão

Abstract

The continental slope off the Amazonas, coast of Pará is a geologically complex region, influenced by tectonic phenomena and sedimentary processes associated with the proximity of the Amazon River mouth. The Amazon River discharges approximately 5.7 × 10¹² m³ of water per year and 1.2 × 10³ m³·s⁻¹ of solid load. The continental slope displays a diverse sedimentary cover distribution, which varies regionally depending on the origin of the sediment sources. Few studies (in sedimentology, palynology, and paleontology) have been conducted on the continental slope of the northern region. The main objective of this study is to analyze the sedimentological characteristics (grain size distribution, calcium carbonate content/CaCO₃, organic matter/OM, and organic carbonate/OC) and investigate the occurrence of fertile sediments in the sediment cover of the upper continental slope off Pará, based on two core samples (T66 and T144). The methodology involved: (1) Bibliographic research on scientific databases; (2) Acquisition of sub-surface core samples using a piston corer; (3) Macroscopic description of cores (color, stratigraphic arrangement, and sediment analysis) and core subsampling; (4) Grain size analysis of the sampled layers, including separation of the silt/clay fraction; (5) Quantification of OM and CaCO₃ contents; (6) Selection of fertile samples for palynological analysis. The results indicate that the sediments are predominantly muddy, with a dominance of coarse silt fraction. They are mostly well-sorted, with approximately symmetrical skewness and platykurtic kurtosis. OM content in the cores ranged from 10.64% to 24.42%, with an average of 16.39% (T66) and 10.64% to 24.42% with an average of 16.39% (T144). Preliminary palynological investigation confirms the presence of pollen grains in the samples. The sediments from the continental slope off Pará consist of a mixture of allochthonous and autochthonous material, with the occurrence of palynomorphs.