辽河西部凹陷曙北地区古近系沙四上亚段滩坝发育的控制因素

Factors Control the Development of Beach Bar in the Upper Fourth Member of the Paleogene Shahejie Formation in the Shubei Area of the Western Sag, Liaohe Basin

滩坝砂体研究是辽河西部凹陷曙北地区断陷湖盆勘探的新领域。文章分析了曙北滩坝砂体的主要控制因素是古地貌、古水深、古物源和古风场等,即"风—源—盆"三端元系统,并提出了定量恢复四个控制因素的方法。结果表明,曙北滩坝主要发育于微观古地貌水下低隆起部位;形成曙北滩坝有利水深大约7 m;滩坝物源来自于三角洲改造、古潜山剥蚀和岸线基岩侵蚀;滩坝的形成受到南北季风影响,风力达8级。根据控制因素将曙北滩坝发育区分为沿岸带、潜山带、潜山披覆带、北部斜坡带和深洼带五个带,其中潜山披覆带最有利于滩坝发育。

Beach bar is a new exploration field for the rifted basins in the Shubei area of the western sag,Liaohe Basin.In this paper,the main controlling factors for the development of the beach bars in the study area were addressed.Results show the factors include the palaeogeomorphology,palaeodepth of water body,palaeosource and palaeowind.These can be summarized as a control system of tri-end members of“wind-source-basin”.The method to quantificationally reconstruct the four factors are proposed.The beach bar in the study area is mainly developed in underwater uplifts.The favorable palaeodepth of water body is approximately 7 m.The palaeosource comes from the transformation of delta,erosion of buried hill and reformation of coastline bedrock.The formation of the beach bar is influenced by the north-south monsoon,the wind force reaching 8th grade.According to the controlling factors,the study area can be divided into five zones,including coastal zone,buried-hill drapping zone,buried-hill draping zone,northern slope zone and deep depression zone,of which the buried-hill draping zone is most favorable for the development of beach bar.