RESTORATION AND BALANCE OF COMPLEX FOLDED AND FAULTED ROCK VOLUMES - FLEXURAL FLATTENING, JIGSAW FITTING AND DECOMPACTION IN 3 DIMENSIONS

Techniques of two-dimensional bed length and cross-sectional area rest oration are extended into true, three-dimensional (3-D) restorations u sing the preservation of areas of individual surfaces plus conservatio n of volume between surfaces. The flexural flattening technique involv es the restoration of a complexly folded surface to a horizontal plane while conserving surface area and minimising finite strain. Multiple surfaces showing superimposed non-co-axial folding may be restored usi ng the flexural flattening method applied to successively deeper surfa ces. In the process of sequential restoration, volumes between the upp ermost flattened surface and underlying surfaces are preserved and the refore the method is volume-balanced. The jigsaw fit of footwall and h angingwall cut-offs of each flattened surface, in map view, provides a unique restoration solution based on a unique translation and/or rota tion of the hangingwall block. Flexural flattening and jigsaw fit perf ormed sequentially on successively deeper surfaces in a three-dimensio nal model may incorporate removal of the uppermost layer and three-dim ensional decompaction at each restoration step. The method is applied to a synthetic 3-D growth fault structure which has been produced usin g multiple discrete slip vectors and bulk simple shear hangingwall def ormation.