Step 1: Understand an unconformity.
An unconformity is a buried erosion surface marking a gap in the rock record. The kinds differ by the rocks above and below.
Step 2: Look at the key clue.
Here the older sedimentary rocks were tilted and eroded before the younger sedimentary rocks were laid on top.
Step 3: Rule out nonconformity.
A nonconformity has sedimentary rocks resting on eroded igneous or metamorphic rock, not on tilted sedimentary rock.
Step 4: Rule out disconformity.
A disconformity separates parallel sedimentary layers with no tilting, so it does not fit the tilted surface here.
Step 5: Identify angular unconformity.
When younger flat-lying beds sit on the eroded surface of older tilted beds, the layers meet at an angle. That is an angular unconformity.
Step 6: Choose the answer.
Angular unconformity, option 2.
\[ \boxed{\text{Angular unconformity}} \]