渤海湾盆地东营凹陷永北地区沙河街组三段砂砾岩粒度概率累积曲线特征及沉积环境意义

沉积水动力条件是沉积相研究的基础，粒度分布特征是分析水动力条件的关键。在岩心精细观察描述和相分析基础上，利用大量粒度分析资料对渤海湾盆地东营凹陷永北地区沙河街组三段砂砾岩粒度概率累积曲线特征及其与水动力机制的对应关系进行了系统研究。研究表明：研究区砂砾岩粒度概率累积曲线主要包括泥石流型、高密度浊流型、低密度浊流型和牵引流型4种基本类型和泥石流-低密度浊流过渡型和高密度浊流-低密度浊流过渡型2种过渡类型。泥石流型包括宽缓上拱式和弧线-直线复合式，反映泥石流沉积特点，多发育在近岸水下扇主水道和扇三角洲平原。高密度浊流型包括悬浮一段式和低斜两段式，反映高密度浊流沉积特点，多发育在近岸水下扇水道、扇三角洲水上及水下分流河道内。低密度浊流型为低斜两段式和低斜两跳一悬式，反映低密度浊流特点，主要发育在近岸水下扇主水道间、辫状水道间。牵引流型包括高斜两段式、滚动-跳跃-悬浮三段式、一跳一悬夹过渡式及两跳一悬式，反映牵引流沉积特点，在近岸水下扇扇中、扇三角洲前缘最发育。泥石流-低密度浊流过渡型为台阶状多段式，反映泥石流向浊流逐渐转化，仅发育在扇三角洲水下分流河道。高密度浊流-低密度浊流过渡型为一跳一斜加过渡式，反映浊流浓度降低的过程，只在近岸水下扇外扇深切水道内发育。

Probability cumulative grain-size distribution curves and their implications for sedimentary environment identification of coarse clastic rocks of the Es3 in Yongbei area,the Dongying Sag,Bohai Bay Basin

Sediment hydrodynamic conditions are the basis of the study on sedimentary facies and the key to hydrodyna-mic analysis is the distribution of grain size.On the basis of elaborate observation of cores and facies analysis,characteristics and its relationship with sedimentary environment of probability cumulative grain-size distribution curves of coarse clastic rocks of Es³ in Yongbei area of the Dongying Sag,Bohai Bay Basin are systematically studied through mass grain size data.The grain-size distribution curves can be classified into 4 basic types(including debris flow type,high-density turbidity current type,low-density turbidity current type and tractive current type) and 2 transitional types(including debris flow to low-density turbidity current transitional type and high-density turbidity current to low-density turbidity current transitional type).The debris flow type includes broad convex arc pattern and arc-linear composte pattern reflecting debris flow deposition,and mostly develops in main channels of inner fan of the nearshore subaqueous fan and the fan-delta plain.The high-density turbidity current type consists of one suspension segment pattern and low-slope two-segment pattern reflecting high-density turbidity current deposition,and develops in channels of the nearshore subaqueous fan and aquatic or subaqueous distributary channels of the fan-delta.The low-density turbidity current type contains low-slope two-segment pattern and low-slope two bouncing segment-one suspension segment pattern reflecting low-density turbidity current deposition,and mainly develops in space between main channels and space between braided channels of the nearshore subaqueous fan.The tractive current type includes high-slope two-segment pattern,one roll segment-one bouncing segment-one suspension segment pattern,one bouncing segment-one suspension segment-one transitional zone pattern and two bouncing segment-one suspension segment reflecting tractive current deposition,and mainly develops in middle fan of the nearshore subaqueous fan and fan-delta front.The debris flow to low-density turbidity current transitional type shows step-like multi-segment pattern representing transition from debris flow to turbidity current and develops in subaqueous distributary channels of the fan-delta.The high-density turbidity current to low-density turbidity current transitional type is of one bouncing segment-one suspension segment-one transitional zone pattern and only develops in deeply-cutting channels of the outer fan on behalf of the density decline phenomenon of turbidity current.