【摘要】 通过露头、钻井岩芯沉积相观察及高频旋回识别,结合全岩碳氧同位素旋回、自然伽玛能谱测井ln(Th/K)值频谱分析及地震反射特征,研究了塔里木盆地塔中—巴楚地区分布的上奥陶统良里塔格组开阔台地及外缓坡相碳酸盐岩中发育的四～六级高频层序(旋回)特征及其叠置关系。认为其六级米级旋回、五级准层序及四级准层序组可能分别与20～40ka、100ka及400ka周期的Milankovitch日-地轨道气候旋回有关,并识别出该区良里塔格组由11～12个400ka周期的准层序组构成。提出海相碳酸盐岩全岩或生物壳碳同位素值可作为反映全球海平面相对变化的指标及识别形成三级层序的主控因素(全球海平面变化、地区性构造沉降-抬升运动)的方法——碳同位素-沉积旋回对比分析法。晚奥陶世良里塔格组沉积时期,塔中台地北缘总体表现为向上变浅的加积型沉积叠置型式,主要与塔中I号断裂活动控制形成的高陡型镶边台地边缘有关;巴楚台地西北缘则表现为向上变浅的加积-进积复合型沉积叠置型式,主要与其断裂活动弱、受沉积作用控制为主的缓坡台地边缘有关。塔中-巴楚台地良里塔格组表现为一个完整三级层序的形成与演化,主要受控于该台地的构造(沉降-抬升)运动而不是全球海平面变化,属于典型的地区性构造层序及不具有全球对比意义。更多还原

【Abstract】 Based on the sedimentary facies and high-frequency cycles observation to outcrop and drilling cores,the characteristics of high-frequency cycles of the 4th,5th and 6th order sequences in the Upper Ordovician Lianglitage Formation platform and nearby slope carbonatic rock in the Tazhong-Bachu area and their stacked pattern are addressed using whole rock C-O cycle,frequency analysis of gamma ray logging and earthquake reflection features.The results show that the 6th order sequence (meter-level cycle),5th order sequence (parasequence) and 4th order sequence (parasequence set) are probably related to the Milankovitch cycles at 20～40 ka,100 ka and 400 ka,respectively,and recognized that the Lianglitage Formation contains probably 11 to 12 parasequence sets with a period of 400 ka cycle.An idea was first proposed that carbon isotope of marine carbonate rock or fossil shell can be used as the good index of global sea level change and the dominant-controlling factors.During sedimentation period of the Lianglitage Formation at the late Ordovician,the northern margin of the Tazhong Platform is characterized by the superimposed deposition,and related to steep margin of the platform controlled by No.1 faulting activity in the Tazhong area,while the northwestern margin of the Bachu platform presents the compound deposition.The Lianglitage Formation distributed in the Tazhong-Bachu Platform embodies the formation and evolution of a complete three level sequence and controlled by the structure of the platform,such as subsidence and uplifting),belonging to a typical of regional structural sequence,and having no global correlation significance.更多还原