Eolian sandstone, Red Head Member, Fundy basin. The main layering in this unit is subhorizontal, and sublayers (cross beds) are inclined to the main layering. This style of cross bedding forms due to the migration of sand dunes, which generally form in an arid or semi-arid climate. Prof. Paul Olsen for scale. Photo by Roy Schlische. Middle: Formation of cross bedding in sand dunes.  Wind blows sand up the up-wind (gentle) slope, which eventually accumulates on the down-wind slope (slip face), forming a new cross bed. Modified from Press & Sevier (1998)Bottom: Modern sand dunes from Colorado. Photo by Louis J. Maher. Additional excellent photos by Prof. Maher are available at his Geology by Light Plane website.