EGU General Assembly 2023
© Author(s) 2023. This work is distributed under
the Creative Commons Attribution 4.0 License.

Orbital control of relative sea level changes in the Plio-Pleistocene of the Northeast Brazilian Equatorial Margin.

Lucas Tortarolo1, Marina Rabineau1, Christian Gorini2, Slah Boulila2, Damien Do Couto2, Tadeu Dos Reis3, and Cleverson Guizan Silva4
Lucas Tortarolo et al.
  • 1Université de Bretagne Occidentale, Geo-Ocean, UMR 6538, 29280, Plouzané, France
  • 2Sorbonne Université, Institut des Sciences de la Terre Paris, ISTeP, UMR 7193, 75005, Paris, France
  • 3Universidade do Estado do Rio de Janeiro, Departamento de Oceanografia Geologica, 20550-013, Rio de Janeiro, Brazil
  • 4Universidade Federal Fluminense, Departamento de Geologia, GGO, 24210-346, Niteroi, Brazil

We address the evolution of the shelf architecture of the Northeast Brazilian Equatorial Margin during the Plio-Pleistocene, using a coupled approach of sequence stratigraphy based on 3D seismic data, and cyclostratigraphy based on well-log data. The main purpose of this study is to highlight the major forcing processes that control evolution and architecture of the shelf during the Plio-Pleistocene.

Our results reveal nine pronounced seismic sequences within the Plio-Pleistocene series, which are correlated to the long 405-kyr eccentricity cycles. Inside the two youngest 405-kyr cycles, we observe nine Falling Stage System Tracts (FSST) matching the short (97-128 kyr) eccentricity cycles. Finally, we identify three major depositional episodes (mega-sequences) in the Plio-Pleistocene: (i) the first episode (from ~4 to ~2.4 Ma) is characterized by small amplitudes of sea-level variations with low to none erosive structures and the absence of clear transgressive series, (ii) the second phase (from ~2.4 to ~0.9 Ma) records a drastic increase of erosional features as well as the apparition of thicker transgressive series and slope failures, and (iii) the third phase (from ~0.9 to present-day) is characterized by a dramatic change in the shelf geometry, most of the sediments are deposited on the slope during FSST while the outer shelf is greatly exposed and eroded during low sea levels. Our results suggest that long-term increase in amplitude of sea level variation is the main driver of the geometrical changes of the Brazilian shelf.  

Boundaries of mega-sequences at 0.9 and 2.4 Ma likely reflect major climatic phases at respectively the Intensification of Northern Hemisphere Glaciation and the Mid-Pleistocene Transition. A significant change in the shelf architecture at around 0.4 Ma, acting as a prominent shift in the depositional system from one prograding to another aggrading, is likely related to the substantial sea-level rise together with the long-lasting Marine Isotopic Stage 11. We conclude that changes in the Brazilian shelf geometry during the Plio-Pleistocene was likely paced by orbitally forced sea-level cycles superimposed on long-term trends and phases in the climate and sea level.

How to cite: Tortarolo, L., Rabineau, M., Gorini, C., Boulila, S., Do Couto, D., Dos Reis, T., and Guizan Silva, C.: Orbital control of relative sea level changes in the Plio-Pleistocene of the Northeast Brazilian Equatorial Margin., EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-227,, 2023.