新疆柯坪大湾沟剖面中-上奥陶统烃源岩高频海平面变化与有机质的关系

通过对柯坪大湾沟剖面中-上奥陶统萨尔干组与印干组页岩的自然伽马测量，建立了此两套页岩的高频海平面变化曲线。同时，对采自于大湾沟剖面的54块泥页岩样品进行了热解与有机碳含量、泥岩X衍射的矿物种类与含量、泥岩密度等分析，将泥页岩样品的分析结果与高频海平面升降变化对比后，认为：①萨尔干组页岩厚13.4 m，属于一个三级层序的海平面升降变化。在萨尔干组页岩的海侵体系域内，发育4次高频海平面升降变化，而在高位体系域内发育3次高频海平面升降变化。印干组页岩厚34 m，也同样属于一个三级层序的海平面升降变化。海侵体系域内发育2次高频海平面升降变化，在高位体系域内则发育6次高频海平面变化。②萨尔干组页岩与印干组页岩均在海平面上升期黏土矿物含量增加，且有机质丰度增高（有机碳含量值增大）。萨尔干组页岩黏土矿物含量高于印干组页岩，碳酸盐矿物低于印干组页岩，其有机质丰度亦高于印干组页岩。③萨尔干组页岩与印干组页岩的黏土矿物成分主要为伊-蒙混层，由于蒙皂石伊利石化是烃源岩催化活性的主要来源，因此富含伊-蒙混合层的这两套烃源岩是最有利的烃源岩。④萨尔干组页岩、印干组页岩均具有海平面上升，有机质丰度增高、泥页岩密度降低和海平面下降，有机质丰度降低、泥岩密度增高的特征。

Relationship between high-frequency sea-level changes and organic matter of Middle-Upper Ordovician marine source rocks from the Dawangou section in the Keping area,Xinjiang

Natural gamma ray measurement was applied to the Saergan shale and Yingan shale from the Middle-Upper Ordovician system in the Dawangou section of the Keping area.On the basis of data obtained from this measurement,variation curves of high-frequency sea-level changes for these two suites of shales were established.Meanwhile,analyses of pyrolysis,organic carbon content,X-diffraction of clay minerals and contents,and mudstone density were performed on 54 mud shales sampled from the Saergan and Yingan formations.A comparison of the analytical results with sea-level changes of the Saergan shale and Yingan shale indicated that: ① The Saergan shale with a thickness of 13.4m remained with a third-order sequence of sea-level changes,4 times and 3 times of high-frequency sea-level changes occurred in the transgressive systems tract(TST) and the highland systems tract(HST),respectively.Similarly,the Yingan shale with a thickness of 34m also fell into the third-order sequence of sea-level changes,but there occurred 2 times and 6 times of high-frequency sea-level changes in TST and HST,respectively.② Both the Saergan and Yingan shales showed an increasing content of clay minerals as sea level rising,which was accompanied with an elevation of organic matter abundance(an increase of TOC).Compared with the Yingan shale,the Saergan shale had a higher concentration of clay minerals and more abundant organic matter but a lower content of carbonates.③ Clay minerals in the Saergan shale and Yingan shale were composed mainly of a mixture of illite and smectite.Since the illitization of smectite into illite supplied the main catalyst for thermal maturation of source rocks,intervals of the Saergan and Yingan shales that were rich in the mixture of illite and smectite would be the best source rock in the study area.④ Both the Saergan and Yingan shales were characterized by an increase of organic matter abundance and a decrease of mudstone density as sea level rising,but a decrease of organic matter abundance and an increase of mudstone density as sea level falling.