四川盆地东部中二叠统茅口组沉积与层序地层特征

Sedimentary and sequence stratigraphic characteristics of Middle Permian Maokou Formation in eastern Sichuan Basin

王文飞

Wang Wenfei

西南石油大学地球科学与技术学院，四川　成都 610500

School of Geosciences, Southwest Petroleum University, Chengdu 610500, China

川东地区中二叠统茅口组碳酸盐岩发育。通过详细观察钻井岩心、野外露头剖面，综合分析测井、录井资料，结合茅口组区域沉积背景，对该区的沉积特征进行了分析。结果表明：该区茅口期主要为浅水型碳酸盐岩开阔台地相沉积，发育深水开阔海、浅水台内滩及较深水滩间海等沉积相带。运用层序地层学方法，确立了该区层序关键界面的识别与划分标志，即隆升侵蚀不整合和海侵水淹没不整合2种层序界面。据此将茅口组划分为3个三级层序，分析了各体系域特征，建立了该区中二叠统茅口组层序地层格架。层序样式以TST（海进（海侵）体系域）大于HST（高水位体系域）为主，说明茅口期具有缓慢海侵、快速海退的特点，层序横向对比良好，川东地区在该期为一稳定的碳酸盐开阔台地沉积；受茅口期末东吴运动地壳强烈抬升影响，PSQ3期层序遭到不同程度剥蚀，保存不完整，局部地区甚至缺失HST期。

Many types of carbonate rocks deposit in the Middle Permian Maoukou Formation of eastern Sichuan Basin. Based on the multidisciplinary analysis of core description, log data, outcrops and Maokou Formation regional sedimentary background, the author analyzes the sedimentary characteristics of this area. The results show that the study area is dominated by shallow water carbonate open platform deposition during Middle Permian Maokou stage, in which sedimentary facies such as deepwater open sea, shallow water beach and deep sea beach developed. Using sequence stratigraphy methods, the recognition and division signal of key sequence boundary are established, namely two kinds of sequence boundaries are identified including uplift erosion unconformity surface and transgression drowned unconformity surface. Based on this, the Maokou Formation in this area is divided into three third?鄄order sequences. Then, the characteristics of each system tract are analyzed and the stratigraphic framework is established. The sequence style is mainly of TST>HST, which reflects the process of a slow transgression?鄄rapid regression in this period and having good sequence lateral comparison. This area is shown as a stable neritic facies carbonate open platform deposition. With the influence of Dongwu Movement in final Maokou stage, PSQ3 sequence is corroded in different degree and saved incompletely and HST in some areas is even missed.

10.6056/dkyqt201502004