Francevillian B Formation

The Francevillian B Formation, also known as the Francevillian Formation or FB2 in scientific research, is a geologic formation of black shale provinces close to the town of Franceville, Gabon from where it gets its name from. The formation was deposited between 2.14-2.08 Ga (billion years ago) in the Palaeoproterozoic, and, uniquely, has not experienced any thermal overprinting due to diagenesis after burial nor significant metamorphism since it was deposited, unlike other formations deposited around the same time. The formation contains possible fossils, including the macroscopic "Francevillian Biota", which has been suggested by some authors to represent the oldest known multicellular organisms, though other authors have questioned the supposed biological origin of the structures, and have suggested that they may instead be inorganic, such as artifacts of diagenesis.