What type of unconformity is formed where the beds beneath the erosional surface are tilted and eroded?

• A. Disconformity
• B. Angular Unconformity
• C. Nonconformity
• D. Paraconformity

Answer: (B)

An angular unconformity occurs when the rocks underneath an erosion surface were previously tilted and eroded, and then younger sediments were deposited on top at a different angle. The tilt and erosion create an angular discordance between the older, tilted beds and the overlying younger beds, which is the hallmark of this unconformity. If the layers above and below were parallel, you’d have a disconformity; if the bottom rocks are non-sedimentary (like igneous or metamorphic) with sedimentary on top, that’s a nonconformity; and a paraconformity resembles a hiatus but lacks obvious surface evidence of tilting or erosion.