Quantifying climate conditions for the formation of coals and evaporites.

Coals and evaporites are commonly used as qualitative indicators of wet and dry environments in deep-time climate studies, respectively. Here, we combine geological records with climate simulations to establish quantitative relationships of coals and evaporites with temperature and precipitation over the Phanerozoic. We show that coal records were associated with a median temperature of 25°C and precipitation of 1300 mm yr -1 before 250 Ma. Afterwards, coal records appeared with temperatures between 0°C and 21°C and precipitation of 900 mm yr -1 . Evaporite records were associated with a median temperature of 27°C and precipitation of 800 mm yr -1 . The most remarkable result is that net precipitation associated with coal and evaporite records remained constant across time. The results here have important implications for quantifying climate conditions for other lithologic indicators of climate and for predicting exogenetic ore deposits.