Clay plug is best described as what geological feature?

• A. A large mound of sediment deposited along the front of a slowly melting glacier
• B. A zone of leaching in soil
• C. A soil deposit developed at the intersection of the oxbow and the new main channel
• D. An O horizon organic matter layer

Answer: (C)

When a river meanders, its old bends can become cut off from the main flow, forming an oxbow. As the river shifts to a new course, fine sediments—especially clay—tunnel into the junction where the abandoned channel meets the active channel. The slow-moving, clay-rich sediment accumulates and effectively “plugs” the old channel, creating a clay-rich soil deposit at that intersection. This is a specific fluvial feature resulting from channel migration and deposition of fine-grained sediment, not a glacial feature, not a zone of leaching, and not an surface organic horizon.