Sole Marks

Sole marks are features that form in the early stages of deposition, usually when a coarser-grained bed, like a sandstone, overlies a finer-grained unit, like a mudstone or shale bed.  These structures often form by erosional processes, followed by deposition, and thus, may show directional features that make them useful in determining paleocurrent direction, in additional to stratigraphic top.  The initial erosion-producing event can result simply from current scour, or may result when an object, called a tool, is dragged by the current across the muddy bottom.  Thus, some sole marks are also known as tool marks.