The paleocirculation of Brazilian Equatorial Margin in the Cenozoic studied from seismic stratigraphy isopach maps
Abstract
The Brazilian Equatorial Margin (BEM) has been in nearly constant latitudinal position for the past 100 million years, being an excellent place to study the oceanography and climatology of the Equatorial Atlantic in the Cenozoic. In this work, we show that the Paleogene and the Neogene have clear differences in the region, and we show the effect of the developing equatorial circulation from the Miocene to the present.
A dataset of 30 seismic lines tied to one oil industry well was used in order to study the Ceará and Barreirinhas Basins in the north shelf of Brazil. The stacked seismic data was tied to the well, time-depth converted and image processed (amplitudes rms, similarity, instantaneous phase). Five seismic horizons were mapped and related to chronostratigraphic markers present on the well. The horizons range from the Maastrichtian to the Serravallian and they were organized in two groups: (1) the Paleogene and (2) the Neogene and Quaternary. Those periods were then studied using isopach and sedimentation rates distribution maps. The center of the BEM comprises the Ceará and Barreirinhas basins and showed different depositional patterns when comparing its west and east portions and also the Paleogene and Neogene. During the Paleogene, we observed higher sedimentation rates to the west of the seamounts chain composing the North Brazilian Ridge (NBR) and also a more homogeneous sediment distribution along the region, indicating that the deep water circulation was weak. During the Neogene and Quaternary, both thickness and sedimentation rates indicate that the shallow and deep water circulation started to develop to its current circulation conditions, reworking sediments driven by the initial acting of the North Brazil Current (NBC) and the Deep Western Boundary Current (DWBC) Using seismic stratigraphy methods we inferred the different deposition patterns in the Paleogene and Neogene in the BEM. In the Paleogene, the deposition was more homogeneous both in shallow and deep waters, with a clear influence of the NBR as a barrier. In the Neogene, the influence of the NBC and DWBC reworked the sediments reaching the basins and increasing the deposition in the platform but still having the NBR as a barrier. The variations of the depositional patterns can be directly related to the main Cenozoic climate events that occurred at both shallow and deep sea.- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2018
- Bibcode:
- 2018AGUFMOS11F1470J
- Keywords:
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- 1641 Sea level change;
- GLOBAL CHANGEDE: 3002 Continental shelf and slope processes;
- MARINE GEOLOGY AND GEOPHYSICSDE: 3022 Marine sediments: processes and transport;
- MARINE GEOLOGY AND GEOPHYSICSDE: 3045 Seafloor morphology;
- geology;
- and geophysics;
- MARINE GEOLOGY AND GEOPHYSICS