Which trap is not exclusively a stratigraphic trap for petroleum?

• A. Pinch-out
• B. Unconformity
• C. Reef
• D. Dipping homocline

Answer: (D)

This question tests the distinction between stratigraphic traps and structural traps in petroleum geology. Stratigraphic traps form from sedimentary processes that create facies changes or surfaces that provide porosity within a sealed geometry—pinch-outs, unconformities, and reefs are classic examples of this type.

A dipping homocline is simply a broad, uniform tilt of the rock layers. It does not by itself create the kind of geological closure needed to trap hydrocarbons. It is a structural feature, and a trap would require additional closure or a seal (such as faulting, folding, or an impermeable layer) to accumulate oil or gas. Because it isn’t inherently a stratigraphic trapping mechanism, it’s not exclusively a stratigraphic trap.