Were the 2.1-Gyr fossil colonial organisms discovered in the Francevillian basin (Palaeoproterozoic, Gabon) buried by turbidites?

The Francevillian series (Gabon) in which the Earthʹs oldest large colonial organisms were recently discovered (El Albani et al., 2010) were deposited 2 Gyr ago. These series are usually interpreted as a fining-upward basin-fill sequence composed by five superimposed lithological terms noted FA to FE. New studies initiated by AREVA, allowed new data to be collected on the southwestern edge of the Francevillian basin, particularly on newly excavated outcrops. Facies interpretations show that the Poubara sandstones and associated shales and black shales (upper part of FB,FB2a), correspond to turbidites deposited on an upper slope rather than one a shelf, submitted to tidal currents or storm wave action. These new interpretations based on facies association, sedimentary geometries, and basin evolution show that the depositional environment could be a turbidite lobe set at a palaeobathymetry deeper than 200 m.