松辽盆地北部上白垩统油页岩地球化学特征及沉积环境初探

松辽盆地北部上白垩统油页岩属中一差油页岩；有机质类型以Ⅰ型为主，Ⅱ.型为辅，处于低成熟一成熟阶段.生物标记化合物都含有丰富的正构烷烃、类异戊二烯型烷烃、萜类化合物和甾类化合物.正构烷烃呈前高后低的单峰型分布，nC₂₃、nC₂₇为主峰碳，重烃组份占绝对优势，OEP值为1.02～6.63，具有明显的奇碳数优势.Pr/Ph比值为0.13～1.37，多数小于0.6，具植烷优势，伽马蜡烷含量较高，油页岩沉积环境为咸化还原环境且盐度较高.萜烷丰度顺序为五环三萜烷>三环萜烷，三环萜烷中C₂₀、C₂₁和C₂₃，丰度相对较高，且C₂₀、C₂₁和C₂₃多呈倒“V”形分布，C₂₃相对富集.甾类化合物主要成份为规则甾烷C₂₇、C₂₈和C₂₉，ααα20RC₂₇、C₂₈和C₂₉甾烷多数呈几乎对称的“V”形分布，C₂₉ >C₂₈ >C₂₇.甾萜烷分布特征反映其原始有机母质构成中既有丰富的菌藻类等低等水生生物，又有一定比例的陆生高等植物混合输入.

A preliminary study on geochemical characteristics and depositional environments of oil shale in the northern Songliao Basin

The Upper Cretaceous oil shale in the northern Songliao Basin might belong to middle and relatively bad one.There were two types of organic matters in the oil shale(Ⅰ and subordinate Ⅱ₁ types ).The oil shale was in the lower-maturity stage, and the maturity of the oil shale in Qingshankou Formation was higher than that of Nengjiang Formation.The biomarker combinations, including n-alkanes, isoprenoid, terpanes and steranes, were similar in the both formations.The n-alkanes showed a dominance of high carbon molecular components with the highest peaks of nC₂₃ or nC₂₇.OEP values of the n-alkanes showed obvious odd carbon dominance.Pr/Ph ratios were 0.13-1.37, which indicated the oil shale possessing phytane dominance.There was a higher abundance of gammacerane in the oil shale.The biomarker's parameters reflected that the depositional environment should be reduction condition,with high salinity.The terpanes distribution patterns of oil shale samples were pentacyclic terpanes> tricyclic terpanes.The terpanes consisted mainly of C₂₀-tricyclic terpanes, C₂₁-tricyclic terpanes and C₂₃-tricyclic terpanes.According to abundance of C₂₃>C₂₁,, the steranes consisted mainly of C₂₇- steranes, C₂₈-steranes and C₂₉-steranes, and the abundance of C₂₉>C₂₇>C₂₈.All these biomarker's characteristics indicated that the organic matters of the Upper Crataceous oil shale in the northern Songliao Basin should be of sigae origin,with proper contribution from terrestrial plant.