Biogeochemical and Environmental Influences on the Composition of Late Archean Kerogens and Extracts

The late Archean (ca. 2.7 Ga) is characterized by widespread occurrence of 13 C-depleted kerogens which suggests microbial methane recycling was a dominant process in the global carbon cycle. In addition, available molecular and isotopic observations for this time suggest that aerobic organisms were present, possibly supported by oxygenated microenvironments within a variety of depositional systems. We propose to evaluate relationships among depositional environments and biogeocheniical signatures recorded in late Archean organic matter for core and outcrop samples of the Tumbiana and Jeerinah Formation and equivalent units in the Pilbara Craton in Western Australia. Our approach integrates sedimentological and stratigraphic observations with analyses of molecular and kerogen isotopic and chemical properties. We will provide observations linking depositional environmental conditions with molecular and isotopic signatures of ancient life and will attempt to test the importance of environmental control on microbial ecosystems and carbon and oxygen cycling on the early Earth.