June 20, 2004
The photo above showing wave ripple marks preserved in Cambrian limestone was taken in October 2000 near the village of Tiout, in the Anti-Atlas Range of Morocco. Ripples are a particular sedimentary bedform generated by unidirectional currents in shallow water. The shape of the ripples depends primarily on a balance between the bedload and the material that is settling from suspension. If there's little suspended load, the ripples tend to be steep. However, if there's a large suspended load, the lee slope builds steadily, forming curved and gentle surfaces. Ripples are dynamic features that change constantly. As ripples migrate down-current, they tend to fill the troughs in front of them. This natural association of troughs and ripples is responsible for the development of small-scale cross-stratification commonly seen in shallow water sedimentary rocks.