 Passive margins are characterised by large prisms of sedimentary material deposited since the original break-up of a continent associated with formation of a new spreading centre.This wedge of material will tend to spread under gravity and, where an effective detachment layer is present such as salt, the extensional faulting that forms at the landward side will be balanced at the front of the wedge by a series of "toe-thrusts".Examples include the outboard part of the Niger delta (with an overpressured mudstone detachment) and the Angola margin (with a salt detachment).