Fig. 4
Illustration of the excess-area graphical technique for different fold types. a Area-height diagram for fault-propagation and detachment folds with the detachment as reference level. b Fault-propagation fold sketch adopted from Suppe and Medwedeff (1990). c Area-height diagram for fault-bend folds with the lower detachment as reference level and d corresponding schematic diagram of a fault-bend fold (Epard and Groshong 1993 after Mitra and Namson 1989). The base excess-area (BEA) construction lines are indicated with dash-dot lines. D total displacement, d displacement across the pin line, h u ramp height, h 1 height of horizon 1, h 2 height of horizon 2, S 1 excess area underneath horizon 1, S 2 excess area underneath horizon 2, ΔS 2 area which moved past the pin line