Sole marks indicate

• A. contact between a sand overlying a clay - sand fills depressions
• B. cross-bedding orientation
• C. ripple marks
• D. fossil burrows

Answer: (A)

Sole marks are impressions on the bottom surface of a sandstone bed that reflect the irregular surface of the underlying mud. They form when sand is deposited over soft clay and flows or loads into depressions in that mud, filling those hollows and leaving characteristic marks on the base. This directly indicates the contact between a sand layer overlying a clay layer and the process of sand filling depressions in the mud. The other features describe different sedimentary structures: cross-bedding records paleocurrent directions within a bed, ripple marks are surface bedforms created by flowing water, and fossil burrows are trace fossils produced by organisms in the sediment.