ASBOG Practice Exam

A disconformity can typically be identified by what visual characteristics?

1. Visible fault lines

2. Complex layers of sediment

3. Horizontal bedding planes

4. Irregular erosion surfaces

The correct answer is: Horizontal bedding planes

A disconformity is a specific type of unconformity where there is a significant gap in the geologic record, representing a period during which deposition stopped and erosion occurred before sedimentation resumed. The visual characteristic that typically identifies a disconformity is the presence of horizontal bedding planes. This indicates that the layers of rock above the disconformity are sedimentary, laid down after the gap, and are parallel to the underlying layers that may have been subjected to erosion. The horizontal aspect of bedding planes suggests an uninterrupted period of deposition following the erosive event that created the disconformity. It shows that sediment was deposited in a relatively stable, uniform environment, reflecting a quiet stage of geological activity. This characteristic stands out compared to other formations where features may become more complex or irregular. Other factors contribute to identifying a disconformity, such as the presence of an unconformity surface, but the horizontal bedding is the most visible and defining feature, making it the best choice in this context.