Early Cretaceous Paleowildfire In Huolinhe Coalfield Of Eastern Inner Mongolia

The study of paleowildfire is a new field in paleoecological research, and has still been rare in China. The present thesis applies the integrated method including of the coal petrology, paleobotany, palynology, stratigraphy, and geochemistry, for the study of the paleowildfire event occurred in Huolinhe during the Early Cretaceous which was recorded in the coal-bearing strata of Huolinhe Coal-Field. The study focuses on the charcoal from the Lower Coal-bearing Member of the Huolinhe Formation in the Huolinhe Coal-Field as the main object of the study, and gained the following achievements.1. The author analyzed the composition of the burned plant charcoal fossils representing the Huolinhe paleowildfire event for the first time, and confirmed conifers as the main charcoal in floral composition, including Phyllocladoxylon, Taxoxylon, Protocedroxylon, and Xenoxylon.2. The author confirmed the types of the paleowildfire events in Huolinhe and the symbols of the various paleowildfires, and confirmed the conifer forest was the main type of the Huolinhe paleowildfires. Meanwhile, a global correlation on the Early Cretaceous paleowildfires has been made.3. The burn temperatures of various types of paleowildfires in Huolinhe are made, including the temperature of charcoal in charcoal-coal is higher (475~550℃), and the temperature of charcoal in peat coal is lower (360~370℃), and charcoal of lignite is between 442℃and 520℃. Based these data, it is suggested that the temperature of the forest crown fire is 442~550℃with the temperature of surface fire in some areas is 360~370℃. 4. Taking the biomark research for this study, confirmed the diterpenoid compounds were as the biomark of the terrestrial plants input, which is based on the fact that the presence of the diterpenoid compounds re?ect the terrestrial higher plants wax origin;and the paleofires were mainly caused by the woody conifers firing . The high content of retene in charcoal indicates a high degree of aromatization, which in turn infers that pyrolysis process at different temperatures with organic molecules changes their structures accordingly.5. Further confirmed the Early Cretaceous Huolinhe flora mainly composed of gymnosperms and ferns, in which the gymnosperms mainly consist of conifers and gingkoales, being both the major coal-forming plants. Fossil wood of 4 genera and 4 species, and spores-pollen of 38 genera and 62 species are newly described, which enriched the recognizing the composition of Early Cretaceous Huolinhe flora.In sum, this thesis used the method of integrated study on wood fossils (charcoals) and coal petrology on the Huolinhe paleowildfire event and its related paleoecological environment. This work is significant for better understanding the coal-forming mechanism and impact of paleowildfire erosion to the coal-forming environment in NE China, and coal-bearing strata correlations in NE Asia. On the other hand, it also benefits the coal-geology study in Inner Mongolia and NE China. The method of interdisciplinary and integrated study in this thesis appears to be a good attempt.