渤海湾盆地东营凹陷始新统红层沉积再认识

渤海湾盆地东营凹陷孔一段—沙四下亚段(孔店组一段和沙河街组四段下部)陆相红层表现为“红—灰组合、以红为主”的地层面貌,有别于过去认为的“全红”,其沉积过程和沉积模式的深入解剖对于了解中国东部始新世早期区域构造古地理特征和古气候演变过程、指导济阳坳陷深层油气资源的勘探和开发具有重要的意义。综合地震、测井、岩心、录井和分析测试资料,对该地层的沉积特征和沉积演化过程进行了深入研究,提出了陆相红层洪水漫湖—时令湖沉积模式。研究表明目的层沉积相类型多样,除了冲积扇、辫状河、洪水漫湖和干盐湖,还包括湖泊、近岸水下扇和风暴相。干旱期发育了冲积扇—洪水漫湖—干盐湖沉积组合,其中在凹陷边缘为冲积扇沉积,向内部过渡为洪水漫湖沉积,在凹陷的北部洼陷带演变为干盐湖。间歇性湿润期主要发育了湖泊沉积,在斜坡带为灰绿色滨浅湖滩坝砂、坝间泥,北部的利津—民丰洼陷演变为半深湖—深湖沉积,凹陷北部陡坡带冲沟部位则发育了近岸水下扇体。推测区域构造古地理、原型盆地特征、古纬度、古物源和古水流方位及周期性变化的古气候条件共同控制了上述地层的发育。

Rethinking the Eocene Red-bed Sedimentation in the Dongying Sag,Bohai Bay Basin

Conventional wisdom assumes red-beds are deposited in the First member of the Kongdian （Ek1） and the Fourth member of Shahejie （Es4x） Formations in the Dongying Sag, Bohai Bay Basin. However, the formation is characterized with red-beds interbedded with greyish green cyclothems, and further revelation of its depositional process and sedimentary model would help in understanding the characteristics of the regional tectono-paleogeography and paleoclimate evolution in eastern China during the Early Eocene, guiding the petroleum exploration and development of the deep layers in the Jiyang Depression. In combination with seismic data, wireline logging, core, cutting, and core testing data, the sedimentary characteristics and evolution have been thoroughly studied in the target formations, and a sedimentary model for flooded lacustrine to seasonal lacustrine deposits in the continental red-bed has been proposed. There are various sedimentary facies in Ek1 and^{Es4x, which include alluvial fan, braided river, flooded lacustrine, player, lacustrine, nearshore subaqueous fan, and tempestites. During the drought periods, facies associations for the alluvial fan, flooded lacustrine, and player were developed, which are distributed in the sag margin, slope area, and sub-sags, respectively. The lacustrine developed during the cyclic humid periods when beach bar sandstones and interbar mudstones were deposited in the slope area and evolved into fairly deep to deep lacustrine deposits in the Lijing-Mingfeng subsag. The northern steep slope area developed subaqueous fans, and it is speculated that the deposition is controlled by regional tectono-paleogeography, basin-prototype, paleolatitude, provenance and paleocurrent, and cyclic variations of the paleoclimate.}