- GeoRef, Copyright 2008, American Geological Institute. Reference includes data from Bibliography and Index of North American Geology, U. S. Geological Survey, Reston, VA, United States
Underwater ripple marks at 400 locations along 21 traverses in Lake Michigan were examined with respect to shape, size, composition and orientation. Conclusions are that shape is primarily a function of relative physical energy and composition; size is controlled by topographic position and grain size; orientation is determined primarily by wind direction and, to some extent, by shoreline direction. Ripple marks are not considered reliable for establishing ancient shoreline directions.