【摘要】 通过对塔里木盆地西北缘巴楚大阪塔格和柯坪水泥厂中—下奥陶统露头剖面的详细观察和研究,并结合塔中地区地震资料对比分析,建立了中—下奥陶统鹰山组至一间房组的高精度层序地层格架和沉积模式。研究表明,中—下奥陶统(鹰山组至一间房组)碳酸盐岩可划分为两个复合(二级)层序(CS1和CS2),其中CS1和CS2又可分出两个和三个三级层序(Sq1—Sq5)。在此基础上依据露头剖面旋回结构变化进一步划分出17~19个高频旋回或四级层序。根据宏观沉积结构和镜下结构特征,总结出的9种微相类型和4种沉积微相组合类型,反映出特定的沉积环境和生物造礁特征,其中包括生物礁-滩复合体、生屑滩、内碎屑滩、氵舄湖和滩间海等。研究还揭示出层序格架中沉积微相组合的发育和演化规律,Sq1—Sq2整体由氵舄湖和滩间海沉积组成,蒸发作用强烈,未见生屑颗粒,发育中细晶白云岩、云质灰岩、含云灰岩等结晶云岩;Sq3时期发育大套厚层内碎屑滩沉积,生屑颗粒开始出现,但数量较少;Sq4时期,砂屑颗粒相对减少,生屑含量大量增加,顶部发育中薄层的生屑滩组合;Sq5时期造礁生物大量出现,以生物礁-滩复合体沉积为主,大致对应于一间房组。更多还原

【Abstract】 The high-resolution sequence structure and depositional model of Yingshan and Yijianfang formations were established by the study of outcrops in Shuinichang of Keping and Dabantage of Bachu in northwestern Tarim Basin combined with 3-D seismic data in Tazhong area. Carbonates in the Middle and Lower Ordovician( Yingshan and Yijianfang formations) can be divided into 2 composite( second-order) sequences( CS1 andCS2),in which CS1 is composed of 2 third-order sequences and CS2 contains 3 third-order sequences. In addition,17 to 19 high-frequency cycles or fourth-order sequences were also identified. Based on macro sedimentary structure and micro characteristics of the outcrops,9 kinds of microfacies and 4 kinds of microfacies combination were concluded to reflect the specific sedimentary environment and reef building characteristics,which contain reef-beach complex,bioclastic beach,intraclastic beach,lagoon and interbank sea. Furthermore,the evolution of microfacies combination was revealed in the sequence structure. Sq1 and Sq2 consist of lagoon and interbank sea with strong evaporation,in which the dolomite and its transition types are common and the bioclast particles are not found. In Sq3 a thick intraclastic beach is developed,and a few bioclasts appear. On the top of Sq4,a middle-thin layer of bioclast beach emerges. In Sq5,the reef-building organism is blooming and consequently the reef-beach complex becomes to be the dominant facies of Yijianfang Formation.更多还原