Effects of paleogeology, chemical weathering, and climate on the global geochemical cycle of carbon dioxide.

摘要

Current geochemical cycling models, utilized to examine atmospheric composition and evolution, rely on estimates of global average rock type, temperature, and precipitation. Consequently, such models cannot assess the sensitivity of global weathering fluxes to changes in the spatial and temporal distribution of climate and geologic exposures. A new method of geologic reconstruction has been developed that determines areas of exposure for each epoch of the Phanerozoic. The paleogeologic maps reveal that the relative proportions of exposed rock types show few abrupt changes through Phanerozoic time, compared to the secular changes in areal extent of rock deposition. However, total exposure area and latitudinal distribution of rock types have changed significantly over at least the past 100 my (the interval for which paleogeography has been factored in) because of eustatic sea level changes and continental drift.;Chemical weathering of silicate minerals acts as a long-term transfer of CO;Mean annual runoff rates are 60% higher at -100 my (using 4x current CO