Tropical laterites, life on land, and the history of atmospheric oxygen in the Paleoproterozoic

摘要: The ca. 2.2 Ga Hekpoort paleosol of the Transvaal Supergroup in southern Africa has been considered a type example and youngest iron-depleted formed under reducing atmosphere early Precambrian. However, mineralogical geochemical data on recently acquired deep drill core intersections indicate that represents part an ancient lateritic weathering profile with pallid lower zone iron-enriched upper zone. Previous studies took place areas where only was preserved from erosion prior to deposition cover beds. laterite is comparable modern tropical laterites oxic presence abundant terrestrial biomass. Revised stratigraphic correlation indicates correlative highly ferruginous profiles Wolhaarkop Griqualand West. This information oxygen-evolution curve, based loss or retention iron paleosols, should be reexamined.