Shallow-water ripple marks at Pinery Park on Lake Huron form perpendicular to the direction of the incoming waves, and hence are sub-parallel to the shoreline. Ripple-mark wavelength decreases away from shore; large ripples, or mega-ripples, occur in elongate depressions parallel to the shore in deeper water.

The breaker zone (about 100 m from shore) is the locus of best sorting; ripple crests are better sorted than troughs. Mean sediment size decreases away from shore, but increases with increasing ripple-mark wavelength. Skewness of samples increases away from shore, but decreases with an increase in mean sediment size. The kurtosis of samples on ripple crests increases away from shore, whereas values for trough samples show no change. Generally, sediments with high kurtosis values are unskewed.

Quartz-grain roundness decreases slightly in the finer sizes. Orientations of grains from ripple-marked sediment are subparallel to the ripple trend. Grain trends on ripple crests show less deviation from the mean than trends in ripple troughs.

The maximum percentage of heavy minerals occurs in the 2 - 2 1/2 range; this may be due to selective removal of quartz grains. Chlorite is concentrated in the finer sizes, probably because its platy habit results in a slower settling velocity. The configuration of light- and heavy-mineral size distribution curves suggests both settling and scouring processes modify the sediment. (Scour is the effect of a moving current on sediment grains at rest on the bottom.) Scour is most intense in the 2 1/2 range, as was indicated by Rubey's general equation (Rubey, 1933) for settling velocities and Airey's equation (as modified by Leliavsky, 1955) for pickup velocity. Settling is the dominant process influencing the distribution of heavy minerals and finer light minerals. The sediment on crests is more scour-modified than that in the troughs. A combined settling and scour process causes the heavy minerals (mostly amphiboles) to segregate into two bands on either side of the ripple crests; the extreme tips of the crests contain few heavy minerals. The prismatic habit of the amphiboles may cause them to be preferentially scoured out of the tips of the crests.

Settling-tube analyses of a scoured sediment, when compared with analyses by other methods, may indicate an apparent fine-skewness, caused by the difference in slope between plots of Airey's equation and Stokes' Law.

Crest and trough sediments are quite similar in grain-size distribution, grain orientation and mineralogy. The differences may occur because the crests project higher into the zone of turbulent water.

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