Petrological Characteristics Of South Hole Of SLCORE Ⅰ For Continental Cretaceous Scientific Drilling Project In Songliao Basin

The scientific drilling of continental cretaceous in Songliao basin named"SLCOREâ… "which is the first scientific drilling of continental cretaceous strata all the world, is the important ingredient of the scientific project called"Major geological events and greenhouse climate change in the cretaceous earth surface system"which is one of national basic research program of china(973 program). In order to discuss the relation between the major geological events of the Chinese continent and greenhouse climate change in the cretaceous, we conduct"SLCOREâ… "in all core recovery, of which main drilling object is the strata of above three stage of Quantou Formation, to seek major geological events in the cretaceous continental basin."SLCOREâ… "is composed of two holes, respectively for the south hole and north hole. Through the continuous drilling core of 944.23 meters from the second member bottom of Nenjiang Formation to the third member top of Quantou Formation in the south hole of"SLCOREâ… ", generalizing the detailed description data about rock core in the drilling field and preliminary analysis of sample in the indoor lab, we study the petrology characteristic of core of the"SLCOREâ… "south hole, summarize detailedly petrofabric characteristics of full drilling core after finishing synthetical histogram of the south hole of"SLCOREâ… ", and analyze paleoenvironment of full rock core based on petrofabric characteristics analysis.Summing up the lithology character of full rock core in the south hole of"SLCOREâ… ", we find some significant results as follows. Firstly, the main lithology character is mud stone whose color has gray, deep gray, olive gray, green gray, brown gray and so on, silty mud stone whose color has gray, green gray, brown gray and so on, argillaceous siltstone whose color has grayish white, gray, green gray, brown gray and so on, siltstone whose color has grayish white,gray, green gray, brown gray and so on, fine sandy rock whose color has grayish white, gray, green gray and so on, and deep yellow brown oil shale. Secondly, the stone of Nenjiang Formation and Qingshankou Formation is almost composed of mud stone except minute quantity of silty mud stone and argillaceous siltstone; mud stone and silty mud stone develop greatly in Yaojia Formation, which accounts for above 90% of total thickness, but a little of argillaceous siltstone and siltstone is found in this Formation; thick ingredient of Quantou Formation develops more greatly than other Formations, because fine sandy rock in the Formation accounts for 10% of total thickness of this Formation. Besides, some interlayer of special lithology character which is not found by conventional segment fetching core can be discovered by full fetching core, such as olive gray dolomite rock interlayer of thin-layer shape or tubercular shape, interlayer of deep gray and gray ostracoda fragmentary rock, calcite interlayer of thin-layer shape, grayish- white and green gray ash interlayer of thin-layer shape.Through the quantitative analysis on type, color, sedimentary structure and biological feature of rock in the south hole of"SLCOREâ… ", this paper draws a figure which reflect the relation between sedimentary environment and petrofabric of full drilling core. The color change curve of our drawing figure is quite fit to a wet-dry change curve which has been drawn by predecessor, which indicates that in some degree the rock color in the south hole of"SLCOREâ… "can reflect paleoclimate characteristics in Songnen basin. Furthermore, this paper discusses origin environment of rock core located in different horizons, and achieves some important conclusions as follows. Firstly, Quantou Formation belongs to fluvial sediment under oxidation and weak deoxidation environment, with semiarid climate feature. Secondly, Qingshankou Formation belongs to semi-deep and deep lake facies sediment under deoxidation environment, with humid climate, and the flow fluctuation is quite frequent. Thirdly, Yaojia Formation belongs to shallow lake facies sediment under weak oxidation andweak deoxidation environment, with subhumid and semiarid climate feature. Flow action in this Formation is stronger than in Qingshankou Formation close to lakeshore. Fourthly, Nenjiang Formation belongs to semi-deep lake facies sediment under strong deoxidation environment, with subhumid climate feature, and the lake depth in this Formation is deeper than the former Formation.