The genetic characteristics of intermittency and continuity in peat formation and accumulation processes

Abstract

The formation and accumulation of peat shows the characteristics of continuity and intermittency. The continuity and intermittency of peat formation and accumulation are actually short-cycle features in the evolution of peat swamp environments. In this study, two basins which were formed during the same period of the Paleogene in China. The coal-forming Huangxian Basin in Shandong Province and the Qiongdongnan Basin were selected for comparative analysis using such methods and techniques as drilling lithology observations and logging comparison data. The Huangxian Basin is a continental lake basin, and the Qiongdongnan Basin is a marginal sea basin in the northern part of the South China Sea. The research results revealed that the Paleogene peat formation and accumulation processes in Qiongdongnan Basin were accompanied by intermittency. As a result, thin coal seams were formed, and the content levels of inorganic substances reached as high as 40%. Those findings indicated that the peat swamp environment of the Qiongdongnan Basin had been unstable and had suffered constant damage. However, the peat formation and accumulation in the Huangxian Basin had a high continuity. As a result, the formed coal seams were relatively thick. The intermittency was manifested as interference caused by changes in the peat accumulation environment, without reaching the level of complete destruction. In addition to the ash yield in the coal, the changes in the sulfur content, ash composition index, and elements in the coal had also reflected the characteristics of sediment and water medium changes during the formation of the coal seams. It was determined that those characteristics had marked the sequential changes of the peat and non-organic matter alternation during the peat accumulation processes, as well as revealing the changes in the peat swamp environmental conditions. This was also one of the manifestations of the continuity and intermittency of the peat accumulation process. It could be ascertained from this study’s experimental results that the intermittency and continuity of the formation and accumulation processes of the peat in the study areas were actually caused by the destruction and reconstruction processes of the peat swamps. Those repetitive processes had formed the observed alternations of peat and non-peat substances, finally resulting in the complexity of the coal seam structures, as well as the overall complexity of the coal compositions in the regions.