山东沂水地区早中寒武世露头层序地层及地层格架

THE OUTCROPPING SEQUENCE STRATA AND STRATIGRAPHIC FRAMEWORK OF EARLY──MIDDLE CAMBRIAN IN YISHUI AREA SHANDONG PROVINCE

山东沂水地区早中寒武世地层同陆表海沉积．根据岩性组合、沉积旋回、岩相、相序以及地层结构、层序界面标志等特征，将区内中下家武统划分９个层序（包括１个Ⅰ型、１个Ⅱ型和７个Ⅱ型展序）和识别出１０个层序界面．Ⅰ型和Ⅱ垫层序均由海侵体系域和高水位体系域组成，凝缩段不甚发育．Ⅲ型层序由凝缩段与高水位体系域组成．地球化学研究表明：微量元素（Ｎｉ，Ｖ，Ｂ，Ｓｒ）含量及Ｓｔ／Ｂａ比值在海侵体系域逐渐增高，在高水位体系域中降低；而δ１３Ｃ，δ１８Ｏ和Ｂａ元素含量和古温度则相反．上述各值在层序界面及附近，一般表现为突变．层序的形成是盆地构造沉降，全球海平面升降、沉积物供应速度及古气候四大因素的综合作用结果．本文建立了Ｆ４断到以西早、中寒武武世地层空间格架，总结了由北向南地层厚度增大，沉积环境由浅到深变化规律．从而明确了岩石地层单位的空间分布关系。

According to the characteristics on the lithological association,depositional cycle.lithofacies,facies sequence,stratigraphic stacking patterns and the signs of sequence boundaries,the early middle Cambrian strata in Yishui area,Shandong provice,which belong to sedimentation of epeiric sea,can be subdivided into 9 sequences(including 1 type-Ⅰ,7type-Ⅱand 1 type-Ⅲ sequences)by 10 sequence boundaries.Type-Ⅰand type-Ⅱsequences are all consisted of transgnessive system tract(TST)and hishstand system tract (HST) with condensed section(CS) not well-developed.Type-Ⅲ sequence is characterized by CS and HST. The studies on their geochemistry show that the contents of Ni,V,B,Sr and the value of Sr/Ba gradually gethigher-in TST and lower in HST:on contrary,the content of Ba and the values of δ13C,δ18O and paleotemperature get lower in TST and higher in HST. On and near the sequence boundaries the above mentioned values and contents change suddenly.The sequences resulted from the subsidence of basin structrres,the elevation and subsidence of global sea level,the supplying rate of sediment,and paleoclimatic conditions.Then the paper sets up the stratigraphic framework of Early-middle Cambrian strata to the west of rift F4,concludes the regular patterns which from north to south the stratigraphic thickness gradually increases and the depositional environment sets deeper,and definitesthe relation ship of spacisl distribution of the lithostratigraphic units.