A stratigraphic trap formed by folding, uplift, and erosion of porous strata, followed by the deposition of later beds which can act as a seal for oil, gas, or water. Although common structures, these traps contain only 4% of the world’s oil, perhaps because of losses that occur during uplift and erosion. See natural gas; petroleum; porosity. Compare anticlinal trap; fault trap; reef trap; stratigraphic trap; structural trap.