Investigação de vales soterrados na plataforma continental do RN utilizando sísmica de alta resolução (Sistema boomer)

Abstract

The high-resolution seismic data processing has been studied, as well as being applied very often in geophysical-geological studies aiming the imaging of Quaternary sedimentary features, as well as of the continental shelf. In the present work, a processing flow was applied in a high-resolution seismic data with the objective of facilitating the identification of incised valleys and interpretation of their filling patterns. Seismic data were collected using a Boomer-type seismic source operating at 300J on the continental shelf of the Potiguar Basin near the municipality of Macau-RN, Brazil. The valleys seen in the sections are morphologically asymmetrical and completely filled. Two incised valleys were identified: one whose maximum incision depth reaches 56 meters while the average width is approximately 360 meters and the filling thickness is around 26.5 meters; and the second valley with maximum depth of incision reaching 76 meters, average width of approximately 1543 meters and filling thickness around 41 meters. In the first valley, the south wall presents slope of 63º while in the north wall the slope is of 59º. In the second valley, the slope in the south wall is 45º and in the north wall of 28º approximately. The sismostratigraphic interpretation allowed the identification of key surfaces, such as the paleovale incision surface, as well as the main horizons and units that comprehend the sedimentary succession that fills the valley. In both the first valley and the second, limited horizons were identified internally in the valley, one of them being the limit of the erosional sequence of the valleys. After comparing the depths of maximum incision of the valleys studied in this study with the incision depths of the Açu and Apodi-Mossoró valleys, it was noticed that the depth of the second valley presented here reached a range of 21 meters more than the Açu and Apodi-Mossoró. In view of this, it was suggested that the incisions of the valleys studied here were triggered during an earlier regression that occurred in the Pleistocene, considering that the incision that gave origin to the valleys presented in this work had a greater depth reach when compared to the incisions of the Açu and Apodi- Mossoró, whose incisions are linked to the Pleistocene regression.