Heterolithic ripple-lamination is most often associated with bidirectional flow. bidirectional flow means that the current direction is stable in one direction for a period of time, and then the current direction changes to the opposite direction. what happens to the velocity of the water when it is changing flow direction? how does this relate to the deposition of the sand and mud? in what type of depositional environment would you expect to heterolithic ripple- lamination to develop?