Expressões sísmicas de correntes de fundo na Bacia do Pará-Maranhão

The continental margin of Para-Maranhao basin is located in the Western Equatorial Atlantic and is characterized by a steep slope cut by canyons, and the proximity of seamounts of the North Brazilian Ridge. Geostrophic currents affect the slope and deeper areas and interact with gravitational processes that control the distribution of sediments into the basin. The objective of this study was to characterize structures produced by ocean bottom currents and downslope processes that are responsible for the construction of the continental margin morphology. The methodology of the present study was based on interpretation of bathymetric maps, seismic sections along the slope and an extensive review about the processes related to geostrophic currents. The results of the study showed that the proximity and alignment of seamounts near the continental slope caused a confinement of bottom currents and consequently its acceleration. This scenario produced sedimentary drifts with mounded geometry, sediment waves, upslope migration of the sediments against the continental slope, and channel related drifts. The onset of bottom currents activities were recognized in pre-Miocene interval. These observations agree with the global modification that has occurred in all ocean basins since Eocene times which is related to tectonic events and the growth of ice caps in high latitudes.