NEOPROTEROZOIC PALEOGEOGRAPHY AND ATMOSPHERIC OXYGEN

I use a coupled climate-biogeochemical model to investigate the geochemical significance, if any, of different paleogeographic reconstructions of the late Precambrian Rodinia supercontinent, especially on atmospheric oxygen concentration. The model includes a fast analytical zonal energy-balance model which accounts for latitudinal and seasonal variation in surface temperatures. Soil depth, soil air oxygen and carbon dioxide concentrations, weathering rates, and recalcitrant soil organic matter content are calculated with latitude. An insolation of 94 percent of the present value is used. Volcanogenic input of carbon dioxide and sulfur dioxide, and burial of organic matter in marine sediments are treated as independent, adjustable parameters. Alternatively, the organic matter burial rate is scaled to the release of phosphorus by weathering of continental rocks. I also investigate the geochemical consequences of (a) the proposed appearance of a late-Precambrian terrestrial soil-forming biota; (b) a putative True Polar Wander-Inertial Interchange event; and (c) a speculatively high Precambrian value of the Earth's obliquity.