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Palinspastic Reconstruction and Forward Modelling |
Department of Geological Sciences and Energy & Minerals Applied Research Center, Campus Box 250, University of Colorado, Boulder, CO 80309, USA
A composite, multi-level salt system from offshore Louisiana is used to illustrate some benefits and limitations of cross section restoration. The system has a complex three-dimensional geometry in which both salt and overburden have apparently moved in multiple directions during Miocene-Pleistocene deformation. Sequential restorations are beneficial in that they provide a framework for: (1) analysis of the structural evolution of salt and overburden; (2) determination of rates of various processes; (3) prediction of changes in the sea-floor paleotopography; (4) evaluation of evolving sediment transport and deposition systems; and (5) analysis of the timing and pathways of hydrocarbon migration. The limitations of section restoration include possible inadequacies of restoration algorithms to model correctly actual rock deformation. More importantly, the assumption of plane-strain deformation is shown to be invalid in this example. Local pin lines are used to demonstrate that there is significant out-of-plane movement. Thus, cross-sectional area for both salt and overburden may need to be added or removed from the section during restoration if the goals are to illustrate the geometric evolution. If, on the other hand, the goal of restoration is to validate and, if necessary, modify the interpretation, then 2D restoration is not appropriate in this case. Ultimately, 3D restoration is needed to restore accurately complex structural geometries.
