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Exoperimental study of estimation for paleohydraulic conditions based on sedimentary structures in strata.

基于地层沉积结构的古水文条件估算实验研究。

基本信息

批准号：
03452069
负责人：
MASUDA Fujio
金额：
$ 2.69万
依托单位：
Osaka University
依托单位国家：
日本
项目类别：
Grant-in-Aid for General Scientific Research (B)
财政年份：
1991
资助国家：
日本
起止时间：
1991 至 1993
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-03452069/
关键词：
flume experiments ripples combined-flow pako-hydroulic condition sedimentary structures ベッドフォ-ム

项目摘要

Generic experiments on combined-flow ripples were carried out to provide detailed criteria of ripples. A recirclating flume with a wave generator was used, in which the direction of unidirectional flows was reversible. Two types of ripples, wave-dominated and current-dominated combined-flow ripples, were recognized based on the ripple roundness. The current-dominated ripples appeared when the unidirectional velocity exceeded approximately 19 cm/sec. The indicative features of combined-flow ripples were revealed as follows : (1) rounded lee and stoss sides, and also rounded troughs were remarkable within the current-dominated ripples. The roundness became stronger as relative magnitude of oscillatory velocity to undirectional velocity became lower. A larger unidirectional velocity often resulted in a higher asymmetry ; (2)the internal structures were characterized by convex-upward foreset laminae, the extremely sigmoidal shape of toes and truncated troughs, for current-dominated ripples. Some of these were recognized in wave-dominated ripples, whose outer forms were very close to that of wave ripples ; and (3) the character of the grain fabric of combined-flow ripples was that preferred imbrication pattern both of the wave- and current-ripples appeared from part to part in a single forest lamina. The unique round profiles resulted from the characteristic movement of sand particles on migrating ripples. The most important phenomenon was vortices generated only beside lee sides of the ripples, caused by the coexistence of the oscillatory and unidirectional components.The experimental results were applied to geologic records to prove those criteria available for the distinction of combined-flow ripples from wave and current ripples, and the estimation of sedimetary processes and depositional environments.

对组合流波纹进行了一般性实验，提供了波纹的详细判据。采用带波发生器的循环水槽，其中单向流动方向可逆。根据波纹的圆度，将波纹识别为波浪主导型和流主导型两种组合流型波纹。当单向速度超过约19 cm/sec时，出现以电流为主的波纹。结果表明：(1)水流主导波纹的背风面、侧翼呈圆形，槽形呈圆形；振荡速度相对于单向速度的相对量级越小，圆度越强。较大的单向速度往往导致较高的不对称性；(2)内部构造以凸出向上的前伏层、极s形的脚趾和截断槽为特征，为水流主导的波纹。其中一些是在波浪主导的波纹中发现的，其外部形式与波浪波纹非常接近；(3)复合流纹的纹理结构特点是在单一森林层中，波浪纹和水流纹在部分到部分之间都呈现出优先的叠瓦状。独特的圆形轮廓是沙粒在迁移波纹上特有的运动造成的。最重要的现象是，由于振荡分量和单向分量的共存，只在波纹的背风侧产生了涡。将实验结果应用于地质记录，证明了这些准则可用于区分组合流纹、波浪纹和流纹，以及沉积过程和沉积环境的估计。