波-流相互作用机制与复合流的沉积构造鉴别标志

Mechanism of wave-current interaction and identification of sedimentary structures of combined-flow

波—流相互作用是复杂水动力条件下流体相互作用的主要方式之一,由波—流相互作用形成的复合流沉积是目前沉积学在流体相互作用这一领域研究较多的一种沉积类型。以已有的文献为基础,对波—流相互作用下细砂级颗粒的运动机制进行了综述,预测了波—流相互作用的沉积特征,总结了复合流的沉积构造鉴别标志。取得的主要认识有:(1)波—流相互作用总体上属于衰弱流(waning flow)悬浮沉积,其微观的沉积机制可分为5种:越过崩落点的喷射沉积(S1)、残余涡动沉积(S2)、未到崩落点的喷射沉积(S3)、背流面的崩落沉积(S4)、垂直降落沉积(S5);(2)波—流相互作用的沉积过程总体上受悬砂量和沉积时间的控制,5种微观沉积机制在不同的悬砂量和沉积时间条件下可形成不同的沉积机制组合,从而导致不同的底床形态;(3)复合流沉积构造鉴别标志主要有:复合流波痕、复合流层理、爬升型复合流层理、不对称丘状交错层理、准平行层理和频繁交替的不能充分发育的浪成波纹层理与流水层理等6类。上述认识对于复杂水动力条件下的沉积学研究及对深水、浅水沉积环境的识别均具有重要的意义。

Wave-current interaction is one of the main types of flow interaction under complex hydrodynamic system,and the deposits of combined flow affected by wave-current interaction is one of the common sedimentary types studied in this area.In this paper,the movement mechanism of fine-grained sand and the sedimentary features under the wave-current interaction are reviewed and predicted,and the identification characteristics of sedimentary structures of combined-flow are summarized.The main conclusions include:(1)wave-current interaction leads to the waning flow suspended deposits in general.The microsedimentary mechanism include:the spray deposit beyond brink point(S1),residual vortex deposit(S2),the spray deposit under brink point(S3),avalanching deposit in the lee side(S4),vertical falling deposit(S5);(2)deposition processes under wave-current interaction are mainly controlled by the suspended sand amount and the deposition time,and the five sedimentary mechanisms resulted in different deposition associations and different morphologies of sea bed;(3)the identification on sedimentary structures of combined flow include:combined-flow ripple,combined-flow-ripple lamination,climbing combined-flow-ripple lamination,asymmetry hummocky cross-bedding,quasi-planar lamination,and frequent alternation of wave-ripple and current-ripple bedding.The studies in this paper are significant for understanding the sedimentology under complex hydrodynamic conditions and the identification of deep-water and shallow water sedimentary environments.