Review and chronostratigraphic calibration of the Barremian–lower Aptian ostracod and pollen/spores biozonations of South Atlantic rift lacustrine formations (Gabon, Congo, Angola): impact on West African-Northeast Brazilian basin correlations

Abstract

Geological syntheses conducted over the last ten years by TotalEnergies on South Atlantic rift basins have led to a reappraisal of the taxonomy and stratigraphy of lacustrine ostracods and terrestrial palynomorphs (spores, pollen) from the Barremian–lower Aptian of West Africa. The results of this revision, based on the acquisition and reinterpretation of data from 55 wells located in North Gabon, South Gabon, Congo and southern Angola-Kwanza basins, are summarized in this publication. The original ostracod and palynological stratigraphic charts have been significantly enhanced. For ostracods, five new zones and fifteen new subzones have been defined, completing the zonation. The taxonomic composition of the assemblages from the six former palynological zones has been clarified, and seven subzones have been described for the first time. Correlations between ostracod and spore-pollen zones of the West African margin, derived from the integration of Gabon and Congo data, have been established from bioevents now considered synchronous at rift basin scale. Their chronostratigraphic calibration, based on the latest International Chronostratigraphic Chart, is improved, supported by radiometric and isotopic data from Northeastern Brazil and the occurrence of distinctive palynomorphs, used as an indirect tool for extra-regional correlation. The present zonal scheme reveals remarkable correspondence between the distribution of ostracods and microfloras on both sides of the rift and reconciles the stratigraphic nomenclature used for the Barremian–lower Aptian in West Africa and Northeastern Brazil. This provides robust correlations between sedimentary formations of basins of the two conjugate margins, especially Recôncavo versus Gabon Interior Basin and South Gabon, Sergipe versus North Gabon, and in the south, Campos versus Kwanza.