Measuring Environmental Factors that Lead to the Development of Coals and Evaporites

Coal was originally formed from plants that require a lot of water or sedimentation. Thus, the coal regions were moist and warm. In contrast, evaporators are formed in dry and hot regions where evaporation is strong. Therefore, coal and evaporators are commonly used as qualitative indicators of wet and dry climatic conditions, respectively, in deep climate studies. However, the quantitative relationships of char and evaporites with temperature and precipitation have not been determined.

In a study published in National Science Review Led by Professor Yong Yun Hu (Department of Atmospheric and Oceanic Sciences, School of Physics, Peking University, China), the authors combined geological records of geological records with climate simulations, establishing quantitative relationships of coal and evaporites with temperature and precipitation during the Eon.

They showed that coaling occurred mostly in the tropical region in the late Paleozoic. This is because the dominant Paleozoic plants were the pteridophytes, which had rather poor water transport capacity and preferred to grow in tropical regions where the climate was warm and humid. Thus, coal formed mainly in the tropics in the late Paleozoic, and the annual mean temperatures and precipitation were 25 °C and 1300 mm, respectively.

In the Mesozoic, gymnosperms became dominant. The internal water transport systems of gymnosperms – secondary xylems – have been developed to be more adaptable to drier, cooler conditions than pteridophytes. As the continents gradually moved into the Northern Hemisphere, plants spread to the temperate, rainy zone at higher latitudes in the Northern Hemisphere. Thus, coal began to form around 50°N in the Mesozoic, with mean annual mean temperature and precipitation of 10°C and 900 mm, respectively.

At the same time, white mold fungi, microbes that feed on lignin, caused the rapid decomposition of lignin. As a result, there was scarce coal in the Mesozoic tropics.

The climate was systematically cooling in the Cenozoic, and precipitation decreased. In this period, angiosperms become dominant, adaptable to the cooler, drier climate of the Cenozoic. Therefore, coal sites and associated with temperature and precipitation are similar to those in the Mesozoic.

Censors always form in the dry subtropical regions of the Northern and Southern Hemispheres in the Eternals. Before the Early Carboniferous, almost all evaporites formed in the southern subtropics because there was a small amount of land in the Northern Hemisphere. The occurrence of evaporation has shifted to the northern subtropics since the late Paleozoic due to the northward movement of the supercontinent Pangea. The annual mean temperatures and precipitation are 27 °C and 800 mm, respectively.

The most notable finding of the study was that net precipitation (precipitation) associated with coal and evapotranspiration remained nearly constant through time, despite drastic changes in global climate during the greenhouse and ice-house periods of the Paleozoic. The average net precipitation value of coal logs was 300 mm per year^-1 For records evaporation was 100 mm per year^-1. This indicates that the physical and chemical processes responsible for the formations of coal and evaporite do not change over time.

The creation of these quantitative relationships can also be used to ‘predict’ the locations of coal and evaporites in the Paleozoic. More than 80% of coal and evaporite records have been successfully forecasted. The results also have important implications for determining climatic conditions for lithological indices of climate and for predicting exogenous ore deposits.