A stratigraphic trap forms due to changes in lithology, porosity, or permeability within the rock record — such as pinch-outs, facies changes, unconformities, or diagenetic seals — rather than structural deformation. Lateral changes in permeability are a primary stratigraphic trapping mechanism. In contrast, structural traps form due to folding (anticlines) or faulting that mechanically seals a reservoir.