孢粉相在下扬子古生界烃源岩研究中的应用
APPLICATION OF PALYNOFACIES TO THE STUDY OF THE PALEOZOIC SOURCE ROCKS IN LOWER YANGTZE REGION
-
摘要: 以下扬子下寒武统幕府山组泥、页岩和下二叠统栖霞组碳酸盐地层为研究对象,运用孢粉相方法,在明确有机质组成的基础上,分析了有机质的来源、类型及烃源岩形成环境。幕府山组有机质组成单一,无定形含量普遍在90%以上,低等水生生物是其主要来源,有机质类型以Ⅰ型为主,烃源岩分布较为集中,TOC高,类型好,是较深水、闭塞、准厌氧到厌氧的泻湖或海湾环境下的产物。栖霞组地层有机质组成变化较大,但仍以无定形为主,类型主要为混合型。由于沉积微环境变化频繁,水体缺氧程度极不稳定,导致栖霞组烃源岩层呈非均质分布,TOC偏低,类型相对较差。Abstract: We discussed the origin, organic-matter type and the formation environments of the source rocks occurred in the Lower Cambrian Mufushan Formation and the Lower Permian Chihsia Formation in the lower Yangtze region upon palynofacies. High quality source rocks with high TOC occur in the Mufushan Formation. They were dominated by over 90% of amorphous organic matter in most of the cases, and predominated by the type I of organic matter mainly from aquatic organisms formed in suboxic-anoxic lagoonal or estuarine environments. The organic matters in the Chihsia Formation are also dominated by amorphous organic matters, but with obvious variations in organic components, so it is of a mixed-type. The frequent change in sedimentary environments and oxygen-deficiency level made the source rocks distributed in a heterogeneous manner with lower TOC and lower quality.