Which trap is not exclusively a stratigraphic trap for petroleum?

The correct answer, which identifies a trap that is not exclusively a stratigraphic trap, is the dipping homocline.

Dipping homoclines are characterized by layers of rock that are inclined but do not necessarily create a specific geological feature that restricts the movement of hydrocarbons like stratigraphic traps do. Stratigraphic traps rely on variations in the rock layers themselves, such as changes in sediment type or deposition patterns, to create a barrier that prevents oil and gas migration.

In contrast, dipping homoclines can also be associated with structural features, such as folds or faults, that can provide additional trapping mechanisms not purely reliant on stratigraphic controls. This means that while a dipping homocline may contain stratigraphic elements, it is not strictly a stratigraphic trap, as it may involve aspects of structural geology that influence hydrocarbon accumulation and migration.

In contrast, traps like pinchouts, solution cavities, and shoestring sands are all examples of stratigraphic traps. Pinchouts refer to the gradual thinning of reservoir rock until it disappears; solution cavities are formed in soluble rocks like limestone, and shoestring sands are sand formations that are often encased in shale, all of which rely on stratigraphic features