浪控三角洲发育特征:以莺歌海盆地东方1-1气田上新统莺二段为例

    GENETIC CHARACTERISTICS OF WAVE-DOMINATED DELTA: A CASE STUDY ON PLIOCENE YING Ⅱ MEMBER IN THE DONGFANG1-1 GAS FIELD,YINGGEHAI BASIN

    • 摘要: 浪控三角洲又可称为鸟嘴状弓形浪控三角洲,目前学术界对其沉积特征的研究较少。以莺歌海盆地莺二段为例,以测井相、地震相以及岩芯相的详细分析为基础,结合研究区沉积背景,揭示了浪控三角洲砂坝的发育特征。岩芯相上,浪控三角洲砂坝主要发育槽状交错层理,还含有少量生物遗迹构造;测井相上主要表现为连续多个反旋回漏斗型沉积层序;地震相上呈现条带状或弓形分布的低角度前积地震相。通过研究莺歌海组二段剖面相和平面相可知,浪控三角洲砂坝平面形态呈弓形,由西向东被泥流水道依次切割为3期沉积,且随着向海方向推进,砂体厚度逐渐增大。浪控三角洲为破坏性三角洲沉积,其形成机理是由于波浪作用大于河流作用,因而沉积模式受波浪改造作用影响较大。

       

      Abstract: Wave-dominated delta, also known as the beak-shaped or bow-shaped wave-dominated delta, has rarely been studied in literatures on its sedimentary characteristics. Taking the YingⅡMember in the Yinggehai Basin of the South China Sea as an example, based on the detailed analysis of logging, seismic and core facies, and combined with the sedimentary background of the study area, the genetic characteristics of sand bars of the wave-dominated delta are described in this paper. On the core facies, the wave-dominated deltaic sand bars are characterized by trough cross beddings with a small amount of lebensspur structures. In the logging curve it shows a series of continuous multiple reverse cyclic funnel-shaped sedimentary sequences. Low-angle progradational seismic facies are observed in bands or bow-shaped deposits. Based on the profile and plane views, it can be seen that the wave-dominated deltaic sand bars have a bow-shaped pattern in plane view, which is successively cut into three parts from west to east by mud flow channels, and the thickness of sand body increases progradationally. The wave-dominated delta is a destructive facies of a delta formed under the action of wave transformation when the wave action is stronger than the river.

       

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