This Figure Shows a Disconformity Between an Upper Dark Layer

question 21

Multiple Choice

This figure shows a disconformity between an upper dark layer (being deposited by the sea) and a lower light-colored layer.What happened to form this disconformity?

• A)The lower layers were tilted and untilted before deposition of the upper layers.
• B)The boundary between the two units indicates that for a time there was either erosion or no deposition.
• C)The lower limestones were converted into another rock type by seawater.
• D)The upper layer must have been deposited by volcanic eruptions.