Abstract
Observations were made on the mode of sedimentation in a settling pond of the Joban Coal Mine, Ibaragi Prefecture, with regard to the development of cyclic sedimentation and ripple marks., From the observed facts, the following three important features were found with regard to the mechanisms of cyclic sedimentation and development of ripple marks: 1) In a steady flow, the cycles all tend to become thinner and also coarser grained from the lower towards the upper., 2) The sediments accumulated in the centre of two vortexs in a turbulent flow tend to decrease in their volume and become coarser in composition than elsewhere., 3) Among five kinds of of ripple marks which developed in the above pond, the wave ripple marks distribute so as to surround each vortex and their branching tips point to each centre., Other ripple marks are developed around the margins of each vortex.,
