东营凹陷沙一段薄层湖相碳酸盐岩成因研究

Genetic research of flaggy lacustrine carbonate in the first Member of Shahejie Formation,Dongying Depression

通过岩心观察、薄片及古生物鉴定,结合岩相、电相及地球化学特征分析,对东营凹陷HB地区沙一段湖相薄层碳酸盐岩成因进行研究。结果表明:目的层纵向上可划分为早、中、晚3期沉积;中期沉积构成了碳酸盐岩的主体,细分为藻礁格架、礁间、礁前、礁后、陆源沙坝和浅湖泥坪等6个成因单元;早期到中期气候、水文条件的改变形成了有利于藻的生长环境,末期海侵作用发生,藻礁建造结束,而广盐性腹足类、介形类生物繁盛,形成了广泛的螺灰岩沉积。

This study focused on the flaggy lacustrine carbonate reservoir in the first Member of Shahejie Formation of the HB area in Dongying Depression. The analysis of the carbonate genesis is through a combination of core observation,thin section and paleontology identification,integration of lithofacies,logging facies,and geochemical characteristics. The results show that the carbonate can be divided into early-stage,mid-stage and late-stage sedimentary bodies. The mid-stage sedimentary body,constituting the principal part of the carbonate,can be further subdivided into the algal frame reef,inter-reef,reeffront,back-reef,continental sandbar and mudflat genetic elements. The suitable environment,resulting from changes of climatic and hydrological conditions,contributes to the flourishment of the algal reef. Because of the transgression in the late depositional stage,the euryhaline snails and ostracoda thrive and widespread snail limestone develops in the late-term sedimentary body,leading to the finality of the algal reef.