Interest in OAEs was originally motivated, in part, by a desire to better understand the processes leading to formation of petroleum source rocks. As we look forward to the end of the Petroleum Era, due to occur in the next century, renewed interest in OAEs has been driven by a very different motivator: the need to better understand the processes and feedbacks involved in rapid perturbations of the Earth’s biogeochemical cycles. OAEs include some of the most geologically rapid and pervasive changes of the oceans and atmosphere driven by changes in the carbon cycle, and they are associated with warm climates, rising sea levels, and possibly increased nutrient fluxes to the oceans. The development of sound environmental policy for the twenty first Century and beyond will depend on our ability to predict the response of the Earth System to anthropogenic CO2 output, the climate warming predicted to result from this output, the increases in sea levels as continental ice sheets continue to melt, and the increase in agricultural runoff of nutrients associated with population-driven expansion of food production. Studies of Mesozoic OAEs provide a critical source of information to our ongoing effort to build accurate and predictive Earth System models.