Question: How would a time in the Earth's supercontinent cycle when there was much formation of oil shale deposits, coals, and limestones affect the carbon dioxide (CO2) concentration in the Earth's atmosphere? a. There would be an increase in the total CO2 in the atmosphere. b. There would be a decrease in the total CO2 in the atmosphere. c. The formation of limestones decreases total CO2, while the formation of oil shale and coal increases total CO2. d. The formation of oil shale deposits, coals, and limestones has very little effect on carbon dioxide