碳酸盐岩台地多旋回沉积小层精细划分对比方法研究——以川中磨溪构造嘉二段为例

以四川盆地川中磨溪构造下三叠系嘉陵江组二段为研究对象,研究海相碳酸盐岩台地多旋回小层精细划分与对比方法。通过对海水咸化旋回、相对海平面变化旋回、古气候变化旋回沉积特征与成因的分析,磨溪地区嘉二段沉积期主要发育潮下型碳酸盐米级旋回层序,沉积界面特征明显并具有一定的成因联系,这种高频沉积旋回具多成因机制特征。在此基础阐明了高频米级旋回的划分原则,提出了一种多旋回沉积界面优选的依据与方法,据此,重新厘定了川中磨溪构造嘉二段小层划分方案。通过精细对比,建立了近于等时的地层格架。该方法有效地避免了单纯运用岩电特征进行地层划分对比时带来的多解性问题,并使各亚段和小层接近于等时的沉积体,为沉积微相及储层的成因和分布研究奠定了可靠的地层学基础。

FINE SUBDIVISION AND CORRELATION OF MULTI-CYCLE CARBONATE PLATFORM SUCCESSIONS:A CASE STUDY OF THE SECOND MEMBER OF THE JIALINGJIANG FORMATION IN THE MOXI STRUCTURE,CENTRAL SICHUAN PROVINCE

The fine subdivision and correlation of multi-cycle carbonate platform successions has been studied using the Second Member(Jia2 Member) of the Lower Triassic Jialingjiang Formation in the Moxi structure of central Sichuan Province as an example.Based on the analysis of the paleosalinity,sea-level change and palaeoclimatic variations,the main cycles of the Jia2 Member are regarded as subtidal Milankovitch cycles.These high frequency depositional cycles have multiple genesis mechanisms.The features of depositional interfaces are described.These depositional interfaces are genetically related.The authors developed the principles for the subdivision of sedimentary cycles in the Jia2 Member,and proposed the optimal basis and methods for the identification of multi-cycle depositional interfaces.The subdivision of the Jia2 Member in the Moxi structure of central Sichuan Basin is revised.Our study effectively avoided the ambiguity of stratigraphic subdivision based solely on rock-electricity property,and the subdivisions are approximately isochronic stratigraphic units.Our results provide a reliable stratigraphic base for the research of the origin and distribution of reservoirs and micro-facies.