塔东南寒武系-中下奥陶统碳酸盐岩台缘带的迁移与相对海平面变化的关系

在岩心、薄片以及测井资料分析的基础上，结合地震相、地震属性以及古地貌来识别台地边缘带，追踪和揭示了塔里木盆地东南部寒武系-中下奥陶统不同期台地边缘相带分布与变迁。台地边缘带发育的岩石类型主要为砂屑灰岩、生屑灰岩、鲕粒灰岩与泥晶灰岩等。台缘滩在地震反射剖面上呈杂乱反射或空白反射特征，礁（丘）滩复合体外部呈丘状外形，内部为显杂乱反射或空白反射。较大的礁（丘）滩复合体快速生长形成地层厚度增大的建隆特征，以及向盆地区沉积厚度急剧减薄形成的陡坡或远端变陡特征是判断台地边缘的证据。应用自然伽马能谱测井资料识别碳酸盐岩岩性和沉积能量的方法，结合有机碳、碳氧同位素等资料，编制塔里木盆地东南部地区的相对海平面变化曲线，探讨海平面变化对不同时期台地边缘相带迁移的控制作用。早寒武世塔东南地区以斜坡-盆地相为主，台缘不发育；中晚寒武世海平面不断下降，台地类型为局限台地，台地边缘相发育且向盆地方向迁移；早奥陶世全球海平面开始上升，蓬莱坝组沉积期台地边缘宽度变窄；鹰山组下段沉积期海平面下降，台地类型变为开阔台地，台地边缘相带变宽；鹰山组上段沉积期经历了快速的水进，海平面又开始下降，台地边缘相带向盆地内侧进一步加宽；一间房组沉积之后随海平面快速上升，台地被淹没。

Migration of the Cambrian and Middle-Lower Ordovician carbonate platform margin and its relation to relative sea level changes in southeastern Tarim Basin

A comprehensive analysis on cores,thin sections and logging data is combined with seismic facies,seismic attri-butes and palaeo geomorphology to identify platform margin and trace the distribution and migration of platform-margin facies belt in southeastern Tarim Basin during different deposition periods of the Cambrian and the Middle and Lower Ordovician.The rock types of platform-margin facies belt are mainly calcarenite,bioclastic limestone,oolitic limestone and micritic limestone.On seismic reflection profiles,platform margin beach facies present as chaotic or blank reflections,and the reef-beach complexes show mound reflection exteriorly and chaotic reflection or blank reflection interiorly.Both the buildup features with increasing stratum thickness caused by rapid growth of large reef-beach complexes,and the steep slope or distal steepening features caused by decreasing stratigraphic thickness in the basin,are indicators of platform margins.The method that uses natural gamma ray spectrometry logging data to identify carbonate lithology and sedimentary energy is combined with the data of organic carbon,carbon and oxygen isotopes,to map the relative sea level changes and their controlling effect upon platform margin migration in different sedimentary periods in southeastern Tarim Basin.Slope-basin facies with under-developed platform margin had dominated the Early Cambrian.With sea level continuously falling during the Middle to Late Cambrian,restricted platform facies started to take shape with edges migrating basin ward.In the Early Ordovician,the platform margin narrowed due to sea level rising during the Penglai Formation deposition and widened as the sea level falling again during the Lower Yingshan Formation deposition.The upper Yingshan Formation experienced rapid transgression which narrowed the platform edge and the lower Yingshanzu Formation went through falling sea level which turned the platform into open ones and widened the platform margin.However,the platform was again submerged as sea level rapidly rising after the deposition of the Yijianfang Formation.