Changes

===Balanced cross sections===

===Balanced cross sections===

Balanced cross sections are used to test the viability or admissibility of a cross section. The deformed cross section is redrawn on a template in the undeformed state so that the beds are unfolded and the offsets on the faults removed ([[:Image:Evaluating-structurally-complex-reservoirs_fig5.png||Figure 5]]). Section balancing requires reference pin-lines and loose lines at opposite ends of the section from which measurements of bed lengths are made. Bed thicknesses and bed lengths are generally retained so that the deformed and undeformed cross sections have the same area. For an ideal restoration, there should be no gaps or overlaps between adjacent fault blocks.<ref name=Woodward_etal_1985 />

Balanced cross sections are used to test the viability or admissibility of a cross section. The deformed cross section is redrawn on a template in the undeformed state so that the beds are unfolded and the offsets on the faults removed ([[:Image:Evaluating-structurally-complex-reservoirs_fig5.png|Figure 5]]). Section balancing requires reference pin-lines and loose lines at opposite ends of the section from which measurements of bed lengths are made. Bed thicknesses and bed lengths are generally retained so that the deformed and undeformed cross sections have the same area. For an ideal restoration, there should be no gaps or overlaps between adjacent fault blocks.<ref name=Woodward_etal_1985 />

Balanced sections were first constructed for thrust belts, but Gibbs,<ref name=Gibbs_1983>Gibbs, A. D., 1983, [http://www.sciencedirect.com/science/article/pii/0191814183900408 Balanced cross section construction from seismic sections in areas of extensional tectonics]: Journal of Structural Geology, v. 5, p. 153-160.</ref> Groshong,<ref name=Groshong_1989a /> and Rowan and Kligfield<ref name=Rowan_etal_1989>Rowan, M. G., and R. Kligfield, 1989, [http://archives.datapages.com/data/bulletns/1988-89/data/pg/0073/0008/0950/0955.htm Cross section restoration and balancing as aid to seismic interpretation in extensional terranes]: AAPG Bulletin, v. 73, p. 955-966.</ref> have successfully applied the method to extensional and salt-related structures. Extensional section balancing is more difficult than compressional balancing because of the bed thickness changes that occur across faults. The balancing template has to show these thickness changes accurately. Generally, computer-aided methods are essential because they can sequentially backstrip the section to remove tectonic as well as compaction strains. Examples of these are described by Rowan and Kligfield,<ref name=Rowan_etal_1989 /> Worrall and Snelson,<ref name=Worrall_etal_1989>Worrall D. M., and S. Snelson, 1989, Evolution of the northern Gulf of Mexico with emphasis on Cenozoic growth faulting and the role of salt, in A. W. Bally and A. R. Palmer, The Geology of North America-An Overview: Geological Society of America, v. A, p. 97-138.</ref> and Shultz-Ela and Duncan.<ref>Schultz-Ela, D., and Duncan, K., 1990, Users manual and software for Restore, version 2.0: The Univ. of Texas Bureau of Economic Geology, 75 p.</ref>

Balanced sections were first constructed for thrust belts, but Gibbs,<ref name=Gibbs_1983>Gibbs, A. D., 1983, [http://www.sciencedirect.com/science/article/pii/0191814183900408 Balanced cross section construction from seismic sections in areas of extensional tectonics]: Journal of Structural Geology, v. 5, p. 153-160.</ref> Groshong,<ref name=Groshong_1989a /> and Rowan and Kligfield<ref name=Rowan_etal_1989>Rowan, M. G., and R. Kligfield, 1989, [http://archives.datapages.com/data/bulletns/1988-89/data/pg/0073/0008/0950/0955.htm Cross section restoration and balancing as aid to seismic interpretation in extensional terranes]: AAPG Bulletin, v. 73, p. 955-966.</ref> have successfully applied the method to extensional and salt-related structures. Extensional section balancing is more difficult than compressional balancing because of the bed thickness changes that occur across faults. The balancing template has to show these thickness changes accurately. Generally, computer-aided methods are essential because they can sequentially backstrip the section to remove tectonic as well as compaction strains. Examples of these are described by Rowan and Kligfield,<ref name=Rowan_etal_1989 /> Worrall and Snelson,<ref name=Worrall_etal_1989>Worrall D. M., and S. Snelson, 1989, Evolution of the northern Gulf of Mexico with emphasis on Cenozoic growth faulting and the role of salt, in A. W. Bally and A. R. Palmer, The Geology of North America-An Overview: Geological Society of America, v. A, p. 97-138.</ref> and Shultz-Ela and Duncan.<ref>Schultz-Ela, D., and Duncan, K., 1990, Users manual and software for Restore, version 2.0: The Univ. of Texas Bureau of Economic Geology, 75 p.</ref>