沉积有机相在陆相层序地层格架中的分布特征--以吐哈盆地台北凹陷及准噶尔盆地南缘中侏罗世煤系为例

综合应用有机岩石学、地球化学及孢粉学的研究方法,对吐哈盆地台北凹陷及准噶尔盆地南缘J2x煤系的沉积有机相在陆相层序的格架中的分布特征进行了探讨。研究表明,一般情况下,各类沉积有机相在层序地层格架纵向上以湖侵体系域为中心对称分布,生烃能力最强的烃源岩出自湖湾-半深湖有机相,其位置一般出现在湖侵体系域中部,向上向下,烃源岩生烃能力依次变差。

The Distribution of Sedimentary Organic Facies in the Continental Facies Sequence Stratigraphic Framework: an example from Middle Jurassic coal-bearingseries in the Taibei sag of the Turpan-Hami basin and Southern Junggar basin

The generation and development of sedimentary organic facies arecontrolled by many factors, such as palaeoclimate, palaeostructure and palaeogeography etc. It is known that these factors have changed periodically in the geological history, and this change must have led to periodical changes of sedimentary organic facies. This can be indicated by distribution of the sedimentary organic facies in the time-stratigraphic framework or sequence stratigraphic framework. Due to the lateral variation in the palaeoenviroments, many types of sedimentary organic facies can develop all over the basin during a single period. The lateral zonation of organic facies can be reflected in their vertical superimposition, which to some extend follows the Walther's law. The sedimentary systems tracts in the sequence stratigraphic framework have been proved to be effective methods to analyze regularities and to predict nature of the organic petrology, organic geochemistry and non-organic geochemistry of the potential source rocks. Based on the above knowledge, the organic petrological, geochemical and palynological mathods have been used to analyze the distribution of the sedimentary organic facies in the continental facies stratigraphic framework of the middle Jurassic coal-bearing series in Taibei sag of the Turpan-Hami basin and the southern Junggar edge. Turpan-Hami and Junggar basins are typical basins of which hydrocarbon generated from coal measure in China and-the continental facies sequence stratigraphic framework in this area have been studied by many scholars and experts. In the muddestone, the organic quantity and potential hydrocarbon-generating ability are indicated by fluorescent organic constituent index, TOC, S1 + S2. The distance from provenance is revealed by SiO2 + AI2O3 content. The deep change of sedimentary media is indicated by Ca/Mg. The salinity and reducibility of media is reflected by Sr/ Ba. Climate change is indicated by P, Sr/Cu, and the both change of the different sedimentary system tract and cycling of the different types sedimentary organic facies can be reflected by all of these change in vertical profile. The results show that, in general, all types of organic sedmentary facies show vertically symmetrical distribution centered at the transgresssives systems trace(TST). The best hydrocarbon source rocks are preserved in the middle part of the TST, and the potential for hydrocarbon generation becomes poor upwards and downwards from this position.