复合流沉积特征的谱系研究现状及其理论框架  

Current Situation of Combined-flow Deposition for Sedimentary Characteristic Series and Its Theory Frame Work

作　　者：李向东[1] LI Xiangdong(School of Land Resource Engineering,Kunming University of Science and Technology,Kunming 650093,China)

机构地区：[1]昆明理工大学国土资源工程学院,云南昆明650093

出　　处：《地球科学进展》2021年第4期375-389,共15页Advances in Earth Science

基　　金：国家自然科学基金项目“阿拉善地块东南缘与鄂尔多斯盆地西缘中、上奥陶统浊流演化及其与内波相互作用研究”(编号:41272119)资助。

摘　　要：复合流由单向流和振荡流叠加而成,属于不同流体相互作用范畴,其研究起源于水槽实验中对复合流波痕的观察,一开始便和沉积学结合在一起。复合流沉积对于复杂水动力条件下的沉积学研究具有非常重要的意义,是目前确定沉积岩沉积时流体相互作用的主要依据。以现有复合流文献为基础,从复合流底床形态与垂向序列谱系、沉积效应与层理构造谱系和泥质底床上的层面构造谱系等3个方面进行了总结。复合流沉积特征受单向流速度和振荡流速度的双重控制,各底床形态及相关的纹层构造均表现出从对称到不对称的连续变化,其不对称程度随单向流速度的增大而增加。垂向序列介于单向衰弱流悬浮沉积和双向振荡流悬浮沉积之间,鲍玛序列和风暴序列是其两个端元类型。复合流沉积虽然以粉砂和细砂颗粒为主,但是在较粗的颗粒中(如扁平砾屑)也可以形成特殊的颗粒组构。在层面构造中,由于单向流和振荡流速度的变化(包括大小和叠加方向)在泥质底床上也会形成不同的底痕谱系。因此,对复合流沉积的研究,将是注重振荡流与单向流相互作用的沉积过程研究,从而有别于传统沉积学在不同沉积环境下的模式研究。Combined flows belong to the interaction between different flows,common with both a unidirectional and an oscillatory component,which were first investigated in flume experiments associated with sedimentology.Deposits of combined flows have great significance in the study of sedimentology in a complex hydrodynamic system,which includes the main evidence for the interaction between different sedimentary flows in rocks.Here we review the deposits of combined-flow from three sections based on present literatures:bed configurations and series of vertical sequences;sedimentary effects of flow and series of cross-bedding structures;and sole marks on muddy substrate.The characteristics of combined-flow deposits are controlled by velocities of unidirectional and oscillatory flow,therefore both the bed configurations and related laminated structures have a continuous variation from symmetric to asymmetric form,and become more asymmetric as the unidirectional flow velocity increases.The vertical sequence is between the vertical stratification produced by suspension of purely unidirectional flow and oscillatory flow,and Bouma sequence and tempestite sequence are their end-member cases,respectively.Although the combined-flow deposits are mainly composed of silt and finegrained sand,some special granular fabric is produced in coarser particles such as plate-like intraclasts.Different spectrum of sole surfaces on muddy substrate is also formed among bed side sedimentary structures because of the variable velocities(including magnitude and superposition direction)of unidirectional and oscillatory flows.Therefore,in the future research area of combined-flow deposits,sedimentary processes research of the interaction of unidirectional and oscillatory flows should be paid much attention,rather than sedimentary mode research for traditional sedimentology based on the various sedimentary environment.

关 键 词：复合流沉积 单向流 振荡流 沉积特征 沉积过程 

分 类 号：P512.2[天文地球—地质学]