Which trap is not exclusively a stratigraphic trap for petroleum?

A dipping homocline is not exclusively a stratigraphic trap for petroleum because it primarily involves structural elements in its formation. Stratigraphic traps are those that are created by changes in rock type or porosity and permeability, often due to sedimentary processes. While a dipping homocline is characterized by layers of sedimentary rock that are tilted, which can influence the reservoir characteristics, it may also involve structural aspects that lead to the accumulation of hydrocarbons due to geological forces rather than purely stratigraphic changes.

In contrast, traps such as pinchouts, solution cavities, and shoestring sands are primarily defined by their stratigraphic nature. Pinchouts occur where a sedimentary layer thins out and can create a reservoir for hydrocarbons. Solution cavities, formed through the dissolution of soluble rocks (like limestone), are also a result of stratigraphic changes. Shoestring sands are elongated bodies of sand that are deposited within a sequence of sediments and are influenced by stratigraphic deposition patterns. Therefore, the primary nature of the dipping homocline as a structural feature sets it apart from the others, which are fundamentally stratigraphic in their formation and function as traps for petroleum.