Geological Record of Atmospheric Evolution

Abstract

The geological history of the atmosphere can be deduced and explored by a combination of theory and observation. The data against which theoretical results can be tested are contained in the sedimentary rock records and include isotopic compositions, trace element concentrations, sediment volumes, and mineralogy, This approach has been followed to study atmospheric evolution, and it is supported by several examples relating principally to the history of carbon dioxide. Paleoclimatic data indicate that the Earth was warm even when the young Sun was faint, From this it is deduced that the early atmosphere was rich in carbon dioxide. High carbon dioxide partial pressures are anticipated for the early Earth because of the absence of stable continental platforms on which to store carbon as long-lived carbonate sediments, In addition, there may be a negative feedback process involving the geochemical cycles of carbon and the carbon dioxide greenhouse that serves to stabilize climate. Geochemical models suggest relatively abundant carbon dioxide during the Cretaceous, consistent with paleoclimatic data that suggest this was a warm period. The warmth may have resulted in relatively high concentrations of atmospheric oxygen during the Cretaceous.