Genetic types of marine source rock in Meso-Cenozoic continental margin basins

Marine source rocks in Meso-Cenozoic continental margin basins are deposited under marine environment, but with complex biogenesis of organic matters. The maceral composition of marine source rocks not only include the sapropelic components representing the input of lower aquatic organisms, but also contain more vitrinite, inertinite and exinite indicating the genesis of terrestrial higher plants. The distribution of source rock biomarker is characterized by binary biogenic input of organic matters, shown as the distribution of saturated n-alkanes dominated by a bimodal state with partial unimodality. The distribution pattern of regular sterane C₂₇-C₂₉ is dominated by asymmetric "V" shape, partially with "L" and anti-"L" shape. Except C₂₃T indicating the input of aquatic organisms, there are distributed oleanane, tricyclic terpane and other tetracyclic terpane with low molecular weight representing the input of terrestrial organic matters. The biogenic compositions of marine source rocks in Meso-Cenozoic continental margin basins are complicated, which is a special phenomenon resulted from the combined effects of marine-continental geological stresses in continental margin basins and dual biogenic input of lower hydrobiont and terrestrial higher plant. Based on biogenic structure, marine source rocks in Meso-Cenozoic continental margin basins can be divided into three genetic types, i.e., endogenous type dominated by algae biogenic input, terrigenous type dominated by higher plant input, and hybrid biogenic type between the both, further revealing the relation between the genetic types of marine source rocks and kerogen types through maceral composition, organic element components and biomarker distribution.