ASBOG Practice Exam

Which of the following best describes the age of sediments in relation to an unconformity?

1. Older sediments are always above younger sediments

2. Younger sediments can cover older erosion surfaces

3. All sediments are of equal age regardless of placement

4. Younger sediments must be older than the sediments below them

The correct answer is: Younger sediments can cover older erosion surfaces

Younger sediments can indeed cover older erosion surfaces, which is a fundamental concept in geology related to unconformities. An unconformity represents a gap in the geological record, often resulting from erosion or non-deposition over a period of time. When younger sediments accumulate on top of these older, eroded formations, it indicates that the younger deposits were laid down after the older sediments had undergone weathering and erosion. This scenario emphasizes how geological processes and time can lead to complex relationships between sediment layers. The older layers that were once deposited could be extensively altered or even partially eroded before the newer sedimentary materials are laid down on top. This layering reflects the dynamic nature of geological processes and the significance of understanding sedimentary sequences in the context of geological time.