沉积学报2025，Vol.43Issue(3)：782-796,15.DOI:10.14027/j.issn.1000-0550.2024.068
砂质辫状河沉积演化机制与沉积构型模式
Sedimentary Evolution Mechanisms and Architecture Models of Sandy Braided Rivers:A study based on quantitative flume experiments
摘要
Abstract
[Objective]During the sedimentation process of sandy braided rivers,the braided channels undergo fre-quent,rapid,and continuous shifts that lead to erosion and reworking within the preserved braided river deposits,such that deposited braided bars and braided channels are characterized by a fragmented morphology,relatively small scale,and undefined quantitative relationships.Traditional sedimentary models of sandy braided river sedimen-tation are inadequate to effectively guide the characterization of subsurface reservoirs.To clarify the sedimentary evo-lution mechanisms of sandy braided rivers and establish a reliable sedimentary architecture model with quantitative size relationships,this study conducted a flume experiment using constant boundary conditions to reproduce the for-mation and evolution of a sandy braided river.[Methods]Using a laser scanner,we obtained topographic data at regular time intervals and accurately reconstructed a three-dimensional sedimentary architecture model of the simulat-ed braided river.Furthermore,the study analyzed sedimentary evolution mechanisms,dissected the sedimentary architecture,and constructed the quantitative size and relationship models for architecture elements.[Results](1)In the initial stage of sandy braided river sedimentation,sediments undergo bedload transportation downstream,forming initial bars.The deflected flow converges into channels,further developing lobe-shaped initial bars,which are then reshaped and organized into a stable network of braided channels and bar patterns through the action of the braided channels.(2)Following the formation of the braided river,the braided channels and bars continually co-evolve,primarily through three mechanisms:lateral accretion of bars driven by braided channels,abandonment and infilling of braided channels overlaying existing bars,and scouring of the confluence by braided channels,which results in downstream bar reorganization.(3)During simulation,bars form within 1 to 6 run steps and grow to their maximum size before experiencing continuous erosion over 3 to 8 simulation periods,ultimately leading to preserva-tion in only 36.28%of the area.(4)Upon completion of the simulation,the internal structure of the braided river deposit is dominated by braided channel deposits,accounting for approximately 57.9%,which can be classified into complex stacked,incised,and isolated channels.Bars often undergo erosion and reworking from channels,presen-ting as smaller,fragmented forms.(5)Within the preserved deposit,the average width-to-thickness ratio of braided channels is 14.1,with an internal accretion ratio of 13.7,whereas for bars,the ratio is 19.8,with an internal accre-tion ratio of 25.4.[Conclusions]This study constructed the complex sedimentary architecture formed within sandy braided river deposits after persistent and intensive erosional modification by the braided channel network,establish-ing a quantitative model of the size and relationships between internal architectural elements and providing a more geologically realistic and quantitative sedimentary architecture model for characterizing subsurface reservoirs.关键词
砂质辫状河/定量化水槽实验/沉积演化/沉积构型/定量规模与关系模型Key words
sandy braided river/quantitative flume experiment/depositional evolution/sedimentary architecture/quantitative scale and relationship model分类
天文与地球科学引用本文复制引用
冯文杰,曹荆楚,张昌民,钱其豪,张涛,雷涛,周志成..砂质辫状河沉积演化机制与沉积构型模式[J].沉积学报,2025,43(3):782-796,15.基金项目
国家自然科学基金项目(41802123,42130813)[National Natural Science Foundation of China,No.41802123,42130813] （41802123,42130813）
