山东东营凹陷南坡地区沙四段纯下亚段湖相碳酸盐岩滩坝发育的控制因素探讨

Controlling factors of carbonate rock beach and bar development in lacustrine facies in the Chunxia submember of Member 4 of Shahejie Formation in south slope of Dongying Sag,Shandong Province

碳酸盐岩滩坝是断陷湖盆中一种重要的沉积类型。文章通过对古气候、古地貌、古物源、古水深和古盐度等因素对碳酸盐岩滩坝形成与分布控制作用进行研究,总结出了"古气候是基础,古地貌和古物源是条件,古水深是关键,古盐度是保障"是东营凹陷南坡地区沙河街组四段纯下亚段碳酸盐岩滩坝的"五古"控制模式。较干旱的温热适中的古气候条件下蒸发作用较强,有利于湖相碳酸盐岩的形成;水下隆起及其斜坡是碳酸盐岩滩坝沉积的有利场所,较低的碎屑岩物源供给指数为碳酸盐岩的发育提供了良好的环境;3～32m左右的古水深是碳酸盐岩发育的主要深度;古盐度为碳酸盐岩的沉积提供了物质保障,在一定程度上控制了白云岩和石灰岩的分布。采用主因素分析法对碳酸盐岩的控制因素进行了排序,古地貌对碳酸盐岩发育的控制作用最大,其次为古物源和古水深,古盐度的控制作用最小。

The carbonate rock beach and bar is an important sedimentation type in rift lacustrine ba- sin. This paper studies the control on the formation and distribution of carbonate rock beach and bar and studies the elements such as the palaeoclimate, palaeogeomorphology, palaeoprovenance, palaeowater depth, palaeosalinity, and puts forward the ＂five-palaeo＂ control model for the submember of Chunxia of Member 4 of Shabejie Formation in south slope of Dongying Sag, such as ＂the palaeoclimate is the back- ground, palaeogemorphology and palaeoprovenance is the condition, palaeowater depth is the key, the palaeosalinity is the guarantee＂. The evaporation in relatively dry and moderate temperature and thermal geologic climate environment is relatively powerful and is favourable for forming carbonate rocks of lacus- trine facies. The subaqueous uplift and slope are the favorable area of carbonate rock beach and bar sedi- mentary facies. The lower degree of clastic rock source providing is the favorable locality of carbonate rocks development. The palaeowater depth of 3-32 m or so is the main area for the carbonate rocks devel- opment. The palaeosalinity offers the substance guarantee for the carbonate rocks development and it con- trols the distribution of the dolomite and limestone. Using the dominant factor analysis the authors make sequence array on the controlling factors. The palaeogeomorphology is the main factor, provenances and palaeowater depth is the secondly, and the palaeosalinity is the factor with the lowest control.