Arrange the sedimentary structures in order of their formation under increasing velocity of water:
A. Lower plane bed B. Small scale ripple marks C. Large scale ripple marks D. Upper plane bed E. Anti dunes
Choose the most appropriate answer from the options given below:

Correct option is D

The sedimentary structures form progressively with an increase in water velocity as follows:
1. Lower Plane Bed (A):
· Formed under low water velocity, where sediment particles settle uniformly on the bed.
2. Small Scale Ripple Marks (B):
· As the velocity increases, ripples form due to the interaction of water flow with loose sediments.
3. Large Scale Ripple Marks (C):
· With further increase in velocity, larger ripples or dunes form as sediment transport becomes more dynamic.
4. Upper Plane Bed (D):
· At higher velocities, the bed becomes flat again due to sediment scouring, forming an upper plane bed.
5. Anti Dunes (E):
· Under the highest velocities, anti dunes form, which are characterized by upstream-migrating bedforms due to high-energy flow conditions.
Information Booster: 1. Bedforms and Flow Velocity:
· Plane Bed (Lower and Upper): Forms under very low or high energy with minimal sediment transport.
· Ripples: Small undulating structures formed by moderate flow.
· Dunes: Larger, spaced features formed by higher energy.
· Anti Dunes: Unique upstream-migrating structures under supercritical flow.
2. Key Factors Influencing Bedform Formation:
· Flow velocity.
· Grain size of sediment.
· Flow depth and turbulence.
3. Sedimentary Structure Applications:
· Used to reconstruct past flow conditions in sedimentary basins.
· Provide insights into environmental energy and depositional environments.
Key Points: 1. The correct sequence reflects increasing flow velocity from lower plane beds to anti dunes.
2. These structures are critical for understanding fluvial and marine sedimentary processes.
3. Anti dunes indicate extreme flow conditions, often in flash floods or steep river gradients.