Sole marks form at the contact between sand and the underlying sediment. Which description matches the formation?

• A. Clay Overlying Sand
• B. Sand Overlying Clay
• C. Silt Overlying Clay
• D. Sand Overlying Sandstone

Answer: (B)

Sole marks are features formed on the bottom surface of a sedimentary bed where it lies on the underlying layer, created by current movement along that interface during deposition. When the contact involves sand resting on top of a softer base, the overlying bed is sand and the underlying layer is clay, i.e., sand overlying clay. This configuration produces the characteristic marks on the base of the sand bed where it contacts the clay, reflecting the flow direction at the time of deposition. The other setups—clay over sand, silt over clay, or sand over sandstone—do not place sand directly on a clay surface, so they don’t match the described formation of sole marks.