曾母盆地古拉让三角洲发育演化定量表征及其控制因素分析

Quantitative Characterization of Evolution and Controlling Factors of Paleo-Rajang Delta in the Zengmu Basin

汤智逸 解习农 徐俊杰 吴佳男 陈北辰

TANGZhiyi XIEXinong XUJunjie WUJianan CHENBeichen

海洋地质资源湖北省重点实验室, 湖北 武汉 430074 中国地质调查局武汉地质调查中心, 湖北 武汉 430205 中海石油(中国) 有限公司深圳分公司, 广东 深圳 518054

Hubei Key Laboratory of Marine Geological Resources, Wuhan, Hubei 430074, China Wuhan Center, China Geological Survey, Wuhan, Hubei 430205, China CNOOC China Limited, Shenzhen Branch, Shenzhen, Guangdong 518054s, China

为了明确南海南部陆缘大型三角洲复合体及陆坡体系的发育演化过程，基于区域二维地震剖面解释，选择进积楔状体迁移角$\alpha$、楔状体加积厚度与进积距离比$\sigma$、楔状体前缘长度$l$及楔状体前缘坡角$\beta$等参数，定量描述了曾母盆地古拉让三角洲演化过程，探究了不同因素对其的控制作用。研究表明，该三角洲主体经历了5个演化阶段：1)早期陆架三角洲发育阶段，形成斜交型进积楔状体；2)快速推进阶段，三角洲演变成陆架边缘三角洲，进积楔状体拐点轨迹呈中高角度迁移，$l$小但$\beta$大；3)稳定加积阶段，沉积中心迁移至陆坡处，进积楔状体拐点呈中角度上升，$l$与$\beta$基本不变。4)缓慢进积阶段，进积楔状体拐点呈低角度进积，$l$与$\beta$逐渐减小；5)晚期陆架三角洲进积阶段。气候条件、物源供给和海平面变迁影响可容纳空间$A$和沉积物供给速率$S$变化，最终共同控制古拉让三角洲沉积体系的发育演化及其陆坡迁移。

To clarify the development and evolutionary processes of the large delta complex and slope system on the southern margin of the South China Sea, this paper, based on the interpretation of 2D seismic profile from the region, quantitatively describes the evolution of the Paleo-Rajang Delta in the Zengmu Basin. Key parameters such as the clinoform migration angle $\alpha$, clinoform accretion thickness to clinoform accretion distance ratio $\sigma$, pro-delta width $l$ and pro-delta slope angle $\beta$ are selected to describe the evolution process of the delta. The study explores the controlling effects of various factors on this process. The main body of the delta has undergone five stages of evolution: 1) the early stage of continental shelf delta, forming an oblique prograding clinoforms; 2) the rapid advance stage. when the delta evolved to the marginal shelf delta, and the inflection point trajectory of the prograding clinoforms rose at a medium-high angle while $l$ was small but $\beta$ was large; 3) the stable accretion stage. when the depositional center moved to the slope, and the inflection point of the prograding clinoforms rose at a medium angle while the front of $l$ and $\beta$ were unchanged; 4) the stage of slow progradation. when the inflection point of the prograding clinoforms presented a low angle of progradation while $l$ and $\beta$ gradually decreased; 5) late stage of shelf delta progradation. when climatic conditions coupled with source supply and sea level change affected the rate of change of accommodation $A$ and the rate of sediment supply $S$ and ultimately jointly controled the evolution of the deltaic system and its slope migration.

10.11885/j.issn.1674-5086.2024.08.28.04