ASBOG Practice Exam

Graded bedding is characterized by what sedimentary feature?

1. Large particles giving way to smaller particles

2. Uniform particle size throughout layers

3. Inverse grading of sediment

4. Presence of organic material

The correct answer is: Large particles giving way to smaller particles

Graded bedding is characterized by a vertical variation in particle size within a single layer of sedimentary rock. This means that large particles are typically found at the base of the layer, gradually transitioning to smaller particles at the top. This feature often results from sediment deposition in a high-energy environment, where larger, heavier particles settle first, followed by progressively finer materials as the energy of the transporting medium decreases. The presence of this gradation in bedding is significant because it provides geologists with insights into the conditions of sediment deposition and the dynamics of the environment at the time. In contrast, sedimentary layers marked by uniform particle size suggest a consistent sedimentation process without varying energy conditions. Inverse grading, where smaller particles are at the bottom and larger ones at the top, would indicate a different depositional environment, such as a turbulent flow event. The presence of organic material, while relevant in some sedimentary contexts, does not define graded bedding specifically. Therefore, the feature of large particles giving way to smaller particles correctly illustrates the characteristic nature of graded bedding.