Interpretação paleoambiental e modelo evolutivo da porção central do complexo deltaico do Rio Paraíba do Sul (RJ)

Abstract

The Paraíba do Sul deltaic complex (PSDC), located on the northern coast of the State of Rio de Janeiro, is a border region between the ocean and the continent that shelters a wide variety of sedimentation environments. The PSDC is stratigraphically positioned at the top of the Campos Basin, encompassing part of its Quaternary sedimentation and is, admittedly, an area of sediment storage for deep waters, which gives it great sedimentological and economic importance. The region has been the target of studies since the 1940s, however, the majority of the work done was based on superficial data and shallow sampling, geophysical data from wells and seismic lines are very scarce, as well as deep wells with continuous sampling. A lack of studies that allow the characterization of the sedimentary succession and its distribution. Based on this, the present work seeks to better understand the evolution of the central portion of the PSDC from information derived from subsurface. For this purpose, 2-TO-1-RJ, 2-MU1-RJ and 2-BG-1-RJ well cores, which were continuously sampled up to 181m, 200m and 410m, respectively, were used. The well cores were analyzed based in facies analysis concepts, with interpretation of sedimentary processes and depositional paleo-environments. Analysis of diffraction of X-rays, total organic carbon (TOC) and palynofacies were performed to evaluate the paleoenvironmental characterization of the 2-TO-1-RJ and 2-MU-1-RJ well cores. From the paleoenvironmental interpretation and characterization the stratigraphic correlation was performed between the three well cores, adopting the maximum flood surface (MFS) as datum. Correlations show that the sedimentation of the central portion of the PSDC was controlled by the high frequency oscillations of the sea level (events of creation and destruction of accommodation space). The forced regressive events (fall of the base level) are responsible for shaping the relief and form important incised valleys that control all subsequent sedimentation. In transgressive events happens the formation of estuaries and lagoons, at the maximum of the penult marine transgression (123,000 years A.P.) there is the installation of a marine environment with deposition of carbonate rocks that mark the MFS. The correlations suggest that neotectonic movement of NW structures occurred and it was responsible for the uplift of the block the left of the study area. Regressive and transgressive events subsequent to the neotectonic reactivation are responsible for the installation of a strandplain, whose age is attributed to about 80,000 years of A.P. Deposits of the last marine transgression (5,100 years old) are recorded