Changes

===Relationship of folding and faulting===

===Relationship of folding and faulting===

Modern theories of structural geology generally relate the formation of folds to accommodation on irregular fault surfaces.<ref name=Hamblin_1965>Hamblin, W. K., 1965, [http://gsabulletin.gsapubs.org/content/76/10/1145 Origin of "reverse drag" on the downthrown side of normal faults]: Geological Society of America Bulletin, v. 76, p. 1145-1164.</ref> <ref name=Dahlstrom_1970 /> Generally, the folds are more obvious on seismic sections than faults, but fortunately there are geometric rules that allow us to predict one shape from the other<ref name=Suppe_1983>Suppe, J., 1983, [http://www.ajsonline.org/content/283/7/684.full.pdf+html Geometry and kinematics of fault-bend folding]: American Journal of Science, v. 283, p. 684-721.</ref> <ref name=Verrall_1982>Verrall, P., 1982, Structural interpretation with applications to North Sea problems: Geological Society of London Course Notes No 3, JAPEC (UK).</ref> <ref name=Gibbs_1983 />; Williams and Vann, 1987<ref name=Williams_etal_1987>Williams, G., and I. Vann, 1987, [http://www.sciencedirect.com/science/article/pii/0191814187900800 The geometry of listric normal faults and deformation in their hanging walls]: Journal of Structural Geology, v. 9, p. 789-795.</ref> <ref name=Groshong_1989a /> in both extensional and compressional examples. An example of a cross section solution explaining the relationship between extensional rollover and listric faults is shown in [[:Image:Evaluating-structurally-complex-reservoirs_fig4.png||Figure 4]].  

Modern theories of structural geology generally relate the formation of folds to accommodation on irregular fault surfaces.<ref name=Hamblin_1965>Hamblin, W. K., 1965, [http://gsabulletin.gsapubs.org/content/76/10/1145 Origin of "reverse drag" on the downthrown side of normal faults]: Geological Society of America Bulletin, v. 76, p. 1145-1164.</ref> <ref name=Dahlstrom_1970 /> Generally, the folds are more obvious on seismic sections than faults, but fortunately there are geometric rules that allow us to predict one shape from the other<ref name=Suppe_1983>Suppe, J., 1983, [http://www.ajsonline.org/content/283/7/684.full.pdf+html Geometry and kinematics of fault-bend folding]: American Journal of Science, v. 283, p. 684-721.</ref> <ref name=Verrall_1982>Verrall, P., 1982, Structural interpretation with applications to North Sea problems: Geological Society of London Course Notes No 3, JAPEC (UK).</ref> <ref name=Gibbs_1983 />; Williams and Vann, 1987<ref name=Williams_etal_1987>Williams, G., and I. Vann, 1987, [http://www.sciencedirect.com/science/article/pii/0191814187900800 The geometry of listric normal faults and deformation in their hanging walls]: Journal of Structural Geology, v. 9, p. 789-795.</ref> <ref name=Groshong_1989a /> in both extensional and compressional examples. An example of a cross section solution explaining the relationship between extensional rollover and listric faults is shown in [[:Image:Evaluating-structurally-complex-reservoirs_fig4.png|Figure 4]].  

[[File:Evaluating-structurally-complex-reservoirs_fig4.png||thumbnail|'''Figure 4.''' Modeling extensional fault shapes from the rollover geometry. (a) the Groshong<ref name=Groshong_1989b>Groshong, R. H., 1989b, Structural style and balanced cross sections in extensional terranes: Houston Geological Society Short Course Notes, Feb. 24-25, 128 p.</ref> method uses oblique simple shear with a reference grid constructed with a spacing equal to the fault heave. Distance 2 from the rollover up to regional elevation of the same reference bed is transferred to 2&prime;; likewise, 2&prime; + 4 is transferred to 4&prime; and so on to complete the fault trajectory. Interpolation between these points is carried out using a half grid spacing. (b) fault trajectory reconstruction by the Groshong<ref name=Groshong_1989b /> method uses simultaneous modeling of three horizons. Dashed trajectories are individual solutions; solid lines are the preferred solution. (From Hossack, unpublished data, 1988.)]]

[[File:Evaluating-structurally-complex-reservoirs_fig4.png||thumbnail|'''Figure 4.''' Modeling extensional fault shapes from the rollover geometry. (a) the Groshong<ref name=Groshong_1989b>Groshong, R. H., 1989b, Structural style and balanced cross sections in extensional terranes: Houston Geological Society Short Course Notes, Feb. 24-25, 128 p.</ref> method uses oblique simple shear with a reference grid constructed with a spacing equal to the fault heave. Distance 2 from the rollover up to regional elevation of the same reference bed is transferred to 2&prime;; likewise, 2&prime; + 4 is transferred to 4&prime; and so on to complete the fault trajectory. Interpolation between these points is carried out using a half grid spacing. (b) fault trajectory reconstruction by the Groshong<ref name=Groshong_1989b /> method uses simultaneous modeling of three horizons. Dashed trajectories are individual solutions; solid lines are the preferred solution. (From Hossack, unpublished data, 1988.)]]