ABSTRACT

Adhesion structures form by the adhering of dry, wind-blown sand to a wet or damp surface. In plan-view morphology and internal structure (in parentheses), three adhesion structures occur: adhesion ripples (climbing-adhesion-ripple structures), adhesion warts (adhesion-wart structures), and adhesion plane bed (adhesion laminations). Related adhesion features are evaporitic-adhesion structures formed with surface salt growth. Experimental growth of adhesion structures in a wind tunnel shows that these types result from subtly different environmental factors; this enhances the value of adhesion structures as tools for detailed paleoenvironmental interpretations. The environmental factors involved are water content, wind direction variability, depositional surface co dition, and the impact angle of saltating grains--a function of local depositional surface slope and wind velocity. The Cambrian Galesville Sandstone, Wisconsin, shows an abundance of adhesion structures; this allows for the recognition of repetitive sequences resulting from the lateral migration of eolian dunes, interdune areas, and marine environments. Adhesion structures also occur in the Ordovician St. Peter Sandstone, Wisconsin, indicating that parts of this enigmatic formation were deposited subaerially.