摘要:
沉积相是沉积物形成条件的物质表现。各种沉积环境受构造、气候等条件的控制,各自具有特殊的物理、化学和生物过程,从而产生具有各种沉积特征的沉积物。沉积相分析是对地层单元进行环境解释的基础。由于沉积岩都已脱离其形成时的环境条件,因此进行沉积岩相分析的前提是建立沉积特征与环境条件之间的联系。这一任务主要通过现代沉积相的研究来完成。这类研究的意义早在十九世纪就由Walther,J提出,并命名为《比较岩石学》(Comparative lithology )，苏联至今沿用此名，西欧各国大多改称为《比较沉积学》( Comparative sedimentology )。比较沉积学的核心是利用现代沉积环境的比较资料对地层单元的古地理环境作综合解释，它是在地貌学、沉积学和沉积岩石学基础上发展起来的一门边缘科学，它的研究对象及其与相邻学科的关系可用图1表示。
Abstract:
The study of sedimentary facies and distribution of groundwater-bearing beds of modern alluvial fans may be applied to reconstruct the palaeogeographic environment and to estimate the rule of enrichment of oil-gas in a fanglomerate oil field.In elongated fault basins,the types of faults along the tR o sides of the basin often differ; one is a single deep-penetrating fault, the other is a series of step-faults.As a result ,the types of alluvial fans which are related to the activity of the faults also differ.They differ distinctively in the thickness and width of the accumulated beds, and in the texture and heterogeneity of the deposits.The alluvial fans related to single deep-penetrating fault are characterized by greater thickness which decre-ases from fanhead to the rim,and by smaller width,coarser pebbles and less heterogeneity of granulo m etry.In such alluvial fans,the difference in lithological cha- racters are mainly present a m ong the subfacies of fanhead,midfan and fanrim.The groundwater is well-distributed in the form of plane. The alluvial fans related to step faults are characterized by minor thickness,w hick increases from fanhead to the rim; by greater width, finer grain size and greater heterogeneity of granulo me- try. The lithology varies across the fan as along its axis.There are channel-flood subfacies and sheetflood subCacies.T he former consists of coarse-grains w hick con-tain little mud,thus presenting greater porosity and being more pervious,forming a belt of ground water-bearing beds. The latter is fine-grained, less pervious and groundwater-poor.It is present as wide slieets on both sides of the channelflood sub facies Through the trend-surface anaysis of the thickness,the clustered analysis of lithology,the size analysis of pebbles and the co m parison of different electro-lithologic profiles. The Third Member of the Upper Wuerhe Formation(Permian)of the No. 5 District of Klamaii Oil Field, }injiang, are considered as the type of alluvi-al fan deposits related to step-faults. The concentration of oil-gas in these fang-lomerates conforms quite well to the distribution of groundwater in modern alluvial fans of the same type.
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