The pattern shown on this sandstone bed is called a sole mark because it was created on the bottom of the sandstone bed. The sandstone bed, therefore, is presently oriented upside down. A rapid, sand-laden current scoured out the pattern on a mudstone bed that was previously underlying the sandstone. As the current waned, the sand grains settled and filled in the pattern that had been created in the mudstone. Then, eventually, the sand grains hardened into rock. The current that created this structure was flowing from upper left to lower right.