Groove Casts

Groove marks are created when a tool is dragged across the surface of a usually muddy substrate.  The tool scours out a groove along the top of the bed, which is later filled in, usually by coarser sediment.  Erosional scour by the tool usually takes place during the early phases of the event depositing the coarser sediment.  Thus, groove marks are considered a primary sedimentary structure.   Groove marks, unlike flute casts, provide only bidirectional paleocurrent information because the shape of the groove is determined by the particular tool scouring the groove, and not by a unique aspect of the current.  Groove marks also provide useful information about depositional stratigraphic relationships.

	This image shows a cross-section through a groove mark.  In this case, the groove is fairly sharp- and steep-sided, but this is not always true.
	Here's a series of grooves indicating paleoflows in a northeasterly-southwesterly direction (assuming north is toward the top).  Note that although some of the grooves end toward the top of the image, it's still not possible to determine whether paleoflows originated from the top or from the bottom of the structure.
	Here's a more complex series of grooves along the base of a bed that was formed under oscillatory flow conditions.  The grooves are established primarily in two cross-cutting directions, probably related to shifting oscillatory flows in the shallow-marine environment.
	This is a unique example of a groove mark.  In this case, it's possible to determine an absolute paleoflow direction because the tool that carved the groove has been preserved along the base of the bed.  The circular object in about the center of the photo is the mold of the tool.  Remember, when looking at sole marking, you're looking at the bases of beds that record features present on the top of the underlying bed.  Thus, a tool protruding from the surface of an underlying bed would be preserved as a depression on the base of the overlying bed.