东营凹陷沙四下亚段沉积环境特征及沉积充填模式

沉积盆地中沉积环境特征控制了砂体沉积成因类型及盆地沉积充填模式。通过对东营凹陷丰深2井、官112井及梁120井沙四下亚段泥质沉积物系统取样，进行全岩X衍射分析和常量及微量地球化学元素分析，在此基础上对东营凹陷沙四下亚段古气候和古盐度指标进行分析。结果表明，古气候指标Rb/Sr比值与石英+长石含量、Cr元素含量及P元素含量呈正比，含量增加反映了气候相对潮湿，与古盐度指标碳酸盐+硫酸盐含量呈反比，其含量增加反映了气候相对干旱。东营凹陷沙四下亚段沉积时期气候干湿交替频繁，气候潮湿时期相对湖平面上升，湖水盐度降低；气候干旱时期相对湖平面下降，湖水盐度升高，使得此时期湖泊呈现为高频振荡性盐湖特征。气候潮湿时期以沉积碎屑沉积物为主，包括冲积扇、浅水型三角洲、滨湖滩坝及近岸水下扇沉积，由于湖水盐度较低，洼陷带主要沉积泥岩、灰质泥岩、含膏泥岩和少量泥质膏岩；气候干旱时期相对湖平面下降，湖泊水体盐度升高，洼陷带以沉积膏盐岩为特征，垂向上具有含膏泥岩、泥质膏岩、膏岩和盐岩的演化序列，平面上表现为由湖泊边缘向湖泊中心发育灰质泥岩、含膏泥岩、泥质膏岩、膏岩和盐岩的环带状结构特征。

Characteristics of Sedimentary Environment and Filling Model of the Lower Submember of the Fourth Member of Shahejie Formation,Dongying Depression

The genetic type of sandbodies and sedimentary filling models were controlled by characteristics of sedimentary environment in sedimentary basin.According to the systematic sampling of argillaceous sediments of Es4x of Well Fengshen 2,Guan 112 and Liang 120 in Dongying Depression,whole rock X-ray diffraction and macroelements and microelements were analyzed,based on which the paleoclimate indexs and paleosalinity indexs of Es4x of Dongying Depression were studied.It turned out that the paleoclimate index Rb/Sr was direct proportion to content of quartz and feldspar,element Cr and element P and inversely proportional to paleosalinity index content of carbonate and sulphate.The increasing ratio of Rb/Sr reflected relatively damp climate,while the increasing content of carbonate and sulphate reflected relatively arid climate.The characteristics of the climate of the period of Es4x of Dongying Depression were frequent damp climate alternate with arid climate.At the period of damp climate,the relative lake level rise and the salinity of lake water decline,while the relative lake level decline and the salinity of lake water rise at the period of arid climate.The characteristics of climate made the lake of Es4x of Dongying Depression have the character of high frequency oscillatory salt lake.Clastic sediments were the main deposits at the period of damp climate,including alluvial fan sediments,shallow water delta sediments,lakeshore beach-bar sediments and nearshore subaqueous fan sediments,and the sag belt mainly deposited mudstone,lime mudstone,gypseous mudstone and a small quantity of argillaceous gypsum rock.At the period of arid climate,the deposition was mainly developed in sag belt and was characterised by gypsum and salt sediments,which have the evolutive sequence of gypseous mudstone,argillaceous gypsum rock,gypsum rock and salt rock upward and the zonal structure with lime mudstone,gypseous mudstone,argillaceous gypsum rock,gypsum rock and salt rock from the margin to the center of the lake in the plane.