【摘要】 塔里木盆地奥陶纪的碳酸盐岩台地发育有长达3千余千米的台地边缘带。通过综合大量的地震、钻井及野外剖面的分析,奥陶纪碳酸盐岩系中识别出4个以不整合面为界的复合(二级)层序。它们均显示出从上超的水进沉积到进积或加积的高位域的沉积结构。其内可进一步划分出10个沉积层序或三级层序。它们的组合和分布决定着碳酸盐台地沉积层序结构的基本特征。沉积层序的水进早期或高位域晚期以颗粒灰岩、生物灰岩等沉积相组合为主;而水进期或高位域早期则以泥晶—粉晶灰岩、簿层白云质灰岩等沉积相组合为主。古地貌恢复并结合钻井资料的沉积相分析揭示出,盆地东北部早、中奥陶世的碳酸盐岩台地边缘的分布受到满加尔深水凹陷的边缘斜坡带古构造地貌的控制,形成一向西凸的弧形碳酸盐岩台地边缘带,沿台地边缘发育有礁—滩沉积复合体。中奥陶世的构造古地理变革使盆内的碳酸盐岩台地分异成塔中、塔北、塘南等多个孤立台地,并由深水、半深水的凹陷所分隔。台地边缘的发育和分布常受古隆起边缘的控制。沿台地边缘的礁、滩相带为重要的有利储集层发育带。中奥陶统中央隆起带缺失中奥陶世早期和晚奥陶世早期沉积,并形成了大范围分布的喀斯特岩溶不整合面。喀斯特岩溶体系以发育垂向的、由断裂控制的串珠状洞穴和多层状分布的岩溶洞穴为特征。跨盆地不同构造带的井—震结合解释剖面的追踪对比表明,盆内与二级、三级层序对应的海进—海退旋回是同时变化的,并与Haq的海平面变化曲线可对比。这反映出盆地范围的或全球海平面变化对沉积旋回结构的发育具有控制作用。盆地西缘露头剖面和盆内钻井岩心的碳、氧同位素分析也为海平面变化的旋回结构分析提供了制约。主要海平面下降期的氧同位素δ18O都发生了明显的正偏。盆内晚奥陶世的海平面总体是呈上升趋势的,晚奥陶世中期海平面的上升导致了盆内碳酸盐岩台地的总体淹没。更多还原

【Abstract】 The Tarim Basin contains extensive carbonate platform deposits of the Ordovician System,with more than three thousand kilometers of rimmed carbonate platform margins. Comprehensive analysis of seismic,borehole and outcrop data reveals that the Ordovician carbonate system in the basin can be divided into four composite sequences defined by major unconformities. Ten sequence consists of a regional depositional cycle from transgression with an onlapping transgressive systems tract( TST) to regression with a prograding highstand systems tract( HST),and can be further subdivided into eight third-order sequences based on subordinate discontinuous boundaries at the carbonate platform marginal zones. Constrained by the marginal slope of the early-rifted Manjiaer aulacogen,the carbonate platform margins of the Lower and Middle Ordovician that prograded eastward in an arcuate belt extending generally northsouth across the northern part of the basin. The development of the Tazhong uplift resulted in an extensive unconformity between the Middle and the Upper Ordovician in the south-central basin,and subsequently constrained the formation of an isolate carbonate platform,with their margins controlled by marginal thrust-fault belts of the paleo-uplift during the Late Ordovician. In the northern basin,the Late Ordovician carbonate platform margin developed around the marginal slope of the Tabei paleouplift. The transgressive regressive cycles of the carbonate system are comparable and seem to have occurred simultaneously across the entire basin,suggesting that the cyclic sequence architecture was fundamentally controlled by eustatic fluctuations. The reef shoal facies complexes that developed along the platform margins,with paleokarst development at unconformities,constitute the major reservoir of large petroleum reserves in the basin.更多还原