Influence of detachment layer thickness on style of thin-skinned shortening

There are several parameters which may determine whether detachment folds or thrust faults develop in thin-skinned compressional systems. A fundamental but little publicised parameter is apparent from consideration of detachment fold growth. As a detachment fold amplifies, its core must be filled by redistribution of ductile material. If the mobile material were insufficient to supply the volume required by the fold core through redistribution, fold growth would be inhibited and eventually faulting would occur. The volume of a detachment fold core is compared here with the volume of available underlying mobile material for various amounts of shortening and sizes of fold. The occurrence of detachment folds versus thrusts in several compressional belts is successfully predicted by this relationship.