Genetic relationship between formation, accumulation and migration and dispersion of peat materials in Paleogene–Take the Qiongdongnan Basin as an example

Abstract

Coal-type source rocks include both coal and terrigenous marine source rocks. By studying the distribution of secondary depressions, uplifts, as well as the characteristics of peat formation and accumulation in the northern marginal sea basin of the South China Sea, and combining them with coal formation characteristics observed in other basins, five genetic theories on the relationship between peat accumulation and dispersed organic matter accumulation are proposed. The northern marginal sea basin of the South China Sea is characterized by “disadvantageous coals formation and favorable terrigenous marine source rocks formation.” This paper provides a distribution map of coal seams and terrigenous marine source rocks in the Qiongdongnan Basin and determines their distribution patterns. Research shows that the migration of sedimentary facies in the basins and inner depressions led to the formation and migration of the peat accumulation centers. In addition, the vertical migration of the peat accumulation centers led to planar migration, which is actually a type of coupling relationship.Previous research results have revealed that the formation of coal-type source rock is multi-phased. The marginal sea basin is composed of several fault-depression basins, with each basin developing a second order of depression and uplift. There is no unified basin center or depositional center to be found. As a result, the concentration centers of coal-forming materials also vary greatly. Based on the distribution characteristics of coal-type source rocks in different basins within the marginal sea basins of the South China Sea, the research results have practical significance and provide guidance for exploring coal-type oil and gas reservoirs in this area.