Late Archean molecular fossils from the Transvaal Supergroup record the antiquity of microbial diversity and aerobiosis

Cores recovered during the Agouron Griqualand Drilling Project contain over 2500 m of well-preserved late Archean Transvaal Supergroup sediments, dating from ca. 2.67 to 2.46 Ga. Bitumen extracts of these strata were obtained using clean drilling, sampling and analysis protocols that avoided overprinting syngenetic molecular fossil signatures with contaminant hydrocarbons. Comparisons of biomarker contents in stratigraphically correlated intervals from diverse lithofacies in two boreholes separated by 24 km, as well as across a ∼2 Gyr unconformity, provide compelling support for their syngenetic nature. The suite of molecular fossils identified in the late Archean bitumens includes hopanes attributable to bacteria, potentially including cyanobacteria and methanotrophs, and steranes of eukaryotic origin. This molecular fossil record supports an origin in the Archean Eon of the three Domains of cellular life, as well as of oxygenic photosynthesis and the anabolic use of O₂.