鄂西建南地区长兴组沉积相及生物礁沉积演化模式
首发时间:2013-09-09
摘要:本文在前人研究的基础上,结合建南地区最新钻井资料和地震解释成果,详细解剖该区长兴组沉积相特征及礁滩体沉积演化模式,提出了长兴组早期发育"碳酸盐缓坡"、中-晚期发育"碳酸盐台地"模式,其中台地模式包括镶边台地和孤立台地,礁滩沉积主要发育于台地边缘相带。建南地区长兴组礁滩分布特征研究表明,南部以滩相沉积为主,北部以礁相沉积为主,其中礁滩沉积体均发育于各层序的高位体系域中,尤以第1个三级层序高位体系域最为发育。该区礁滩沉积是在相对海平面不断下降的背景条件下形成的,形成了一套规模较大的加积-进积型台地边缘生物礁、滩沉积序列。主要礁滩发育期可分为三个演化阶段,第一阶段以小规模低能滩相沉积为主,也是生物礁奠基阶段;第二阶段为大型障积型生物礁和生屑滩发育期;第三阶段为生物礁逐渐消亡阶段,该期生物礁以粘结-障积型生物礁为主。礁滩发育晚期的暴露浅滩白云石化作用强烈,形成良好储集岩。
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Sedimentary Facies Characteristics and Evolution Model of Reef Deposition in Jiannan area of Western Hubei
Abstract:Based on the previous researches, combined with recent drilling data and seismic interpretation of Jiannan area in western Hubei province, characteristics of sedimentary facies and evolution model of reef-bank of Changxing Formation were studied in detail. At the early and middle-late stage of Changxing Formation, carbonate ramp and platform are developed respectively, of which the carbonate platform model include rimmed platform and isolated platform, and reef-bank deposits are mainly developed in the platform margin. The distribution characteristics of reef and bank of Changxing Fomation shows that reef facies is mainly located at the north part of study area, and bank facies usually developed in the south. In the HST of each sequence, especially the first third-order sequence, reef-bank deposits are widely developed. As the relative sea level fall gradually, reef-bank deposits forms a set of large-scale aggradational or progradational sedimentary succession. The development of reef and bank can be devided into three phases. During the first stage, low-energy bank deposits, developed on a small scale, are the basis of subsequent reefs. Large-scale baffle reef and bioclastic bank are formed at the second stage, and decayed at the third stage, when bind-baffle reefs are developed. During the late stage for reef and bank development, favorable resevoir of Changxing Formation in study area is formed by extensive dolomitization of exposured shoals.
Keywords: Jiannan area Changxing Formation sedimentary facies reef deposits evolution model
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