东营凹陷东部始新世三角洲供给型重力流沉积特征与模式

基于岩相分析、流体成因解释、平面沉积相和同生断层编图,对渤海湾盆地东辛地区始新统湖相三角洲供给型浊积体系的沉积特征及沉积模式进行研究。结果表明:研究区发育滑动、滑塌、碎屑流和浊流4类9种深水异地沉积过程;三角洲前缘斜坡脚和同生断层下降盘控制了滑动、滑塌体,而断层活动微弱的深水低洼区控制了碎屑流沉积;由于深水沉积区规模小,以及同生断层对局部地貌的控制,深水搬运距离短,导致从滑动、滑塌到浊流的流体转换过程发育不完整,形成以碎屑流或滑塌为主的深水沉积体系;碎屑流主控下的重力流水道可能因为滑水搬运机制而缺乏连续性砂岩沉积;研究有助于深化陆相三角洲供给型重力流沉积的理解,也能为该类砂岩储层的有效预测提供地质模型。

Sedimentary characteristics and model of delta-fed turbidites in Eocene eastern Dongying Depression

Based on lithofacies analysis, original interpretation and mapping of sedimentary facies and growth faults, the dominating sedimentary process and depositional model of delta-fed turbidites are studied for the Eocene Dongying Depression, Bohai Bay Basin. The results show that there are four deep-water sedimentary processes in the study area:slide, slump, debris flow and turbidity current, which can be further subdivided into nine deposition types. Slide and slump are generally restricted to the foot of delta front and the down-wall side of growing faults with strong activities, while debrites usually deposit at low-lying areas with weak fault activity and far from foot of delta front. Transportation distance of gravity flow in the study area is short due to restriction by small-scale deep water area and local landform controlled by activities of fault, which lead to incomplete development of gravity flow from slide, slump to turbidity current. As a result, there is a possible lack of continuous sandstone in gravity flow channels caused by "hydroplaning" of debris flows. These findings are helpful to understand sedimentary characteristics of turbidites fed by lacustrine delta, and have significant applications in prediction of turbidites sandstone reservoir.