The impact of Quaternary sea-level changes on the sedimentary organic matter of the Paraíba do Sul Deltaic Complex area, southeastern Brazil

Abstract

The Paraíba do Sul Deltaic Complex (PSDC) landscapes diversified markedly over the last 123,000 years B.P. The PSDC is characterized by non-marine to marine deposits, and very complex non-marine deposits in its uppermost part. In such a setting, the characterization of the sedimentary organic matter is a useful tool for conduction paleoenvironmental reconstruction. Sea level changes during this interval are reflected in the stratigraphic distribution of sedimentary organic matter recorded in the four sections of the onshore portion of Campos Basin, southeastern Brazil. The succession is dominated by the woody material (phytoclasts), related to a continuous terrigenous input on the area and is characterized by a long-term regressive trend. The stratigraphical distribution of five palynofacies association reveal a wide variety of depositional paleoenvironments. The palynofacies associations attributed to alluvial fan, fluvial, shallow marine and lagoon were recognized. The alluvial fan, in the lowermost part of the succession, is characterized by high contents of opaque and pseudoamorphous particles. The fluvial deposits, in the lower and uppermost parts of the succession, are dominated by wood material (non-opaque) and sporomorphs. The marine deposits (shallow marine and lagoon), in the middle parts of the succession, appear to be related to the dinoflagellate cysts, microforaminifera linings and amorphous organic matter and suggest a notable marine incursion.