What geometric form do sole marks create on the underlying substrate?

• A. Convex wavelike forms
• B. Concave depressions
• C. Flat bedding planes
• D. Vertical ridges

Answer: (A)

Sole marks form on the bottom surface of a sediment layer when a current or objects trundling along the bed interact with the substrate during deposition. As the bed presses down and drags across the underlying surface, the contact and movement create rounded, arching imprints rather than flat or incised features. That interaction tends to leave convex, wavelike elevations on the substrate, reflecting the curved contact between the moving load and the ground. So the underlying surface shows convex, wavelike forms.

Flat bedding planes would lack such imprinting, vertical ridges imply a different tectonic or deformation process, and concave depressions would be grooves or pits rather than the upward, rounded impressions produced by sole marks.