Exploration of Cross Stratification and Bedforms
Cross stratification and cross lamination (same thing, but on a smaller scale) form as dunes and ripples (bedforms) migrate, leaving behind some of the sediment. The style of cross stratification that is preserved in a rock depends on the shape of the bedform, which direction it is migrating, and the amount of sediment left behind (deposited). You have a number of different examples of cross stratification in the lab samples. Here, you can use some movies and look at photos of additional samples to interpret the types of bedforms that created the cross stratification in your samples.
The three resourses that will help the most with your lab are: 1) the lab text, Sedimentology in the Field; 2) the photos of sedimentary structures and 3) Bedform migration movies from the USGS Bedform Sedimentology web site.