ABSTRACT: Forward and Reverse Modeling of Extensional Sedimentary Basin Formation: Application to the North Sea Basin

NEWALL, M. J., Koninklijke/Shell Exploratie en Producktie Laboratorium, Rijswijk, Netherlands, and N. J. KUSZNIR, University of Liverpool, Liverpool, U.K.

A combined forward and reverse extensional sedimentary basin modeling technique has been developed and applied to data from the North Viking Graben, Shetland Platform, Haltenbank, and Danish Central Graben within the North Sea Basin. Present-day cross sections are reverse modeled to the base of the postrift sequence using flexural backstripping, decompaction, and reverse thermal subsidence modeling. A flexural cantilever coupled simple-shear/pure-shear model is used to forward model synrift basin evolution and erosion. The results of forward and reverse modeling are compared at the end of the rifting and erosion/base of postrift, and the models are iterated until a good fit is achieved. This coupled forward and reverse modeling technique allows effective elastic thickness (lithosphere flexural strength) to be well constrained, which is essential if reliable estimates of the beta stretching factor profile, paleo-bathymetry, and paleo-emergence are to be made.

The flexural cantilever coupled simple-shear/pure-shear model used in the forward model assumes that the continental lithosphere deforms by planar faults in the upper crust and by plastic pure-shear in the lower crust and mantle. During extensional faulting, the footwall and hanging wall blocks are assumed to behave as two interacting flexural cantilevers. The flexural response of the two cantilevers generates footwall uplift and hanging wall collapse. For a set of adjacent planar faults, the lateral superposition of flexural footwall uplift and hanging wall collapse generates domino-style block rotation faulting.

Application of the coupled forward and reverse modeling technique to the North Sea Basin shows that the Late Jurassic rift of the North Sea was a rapid extension event with a stretching factor of less than 1.25 and that the continental lithosphere responded to extension with an effective elastic thickness of between 3.0 and 4.5 km. Footwall uplift and erosion in response to extension were significant and water depths of over 1.0 km were common in sediment-starved grabens.

AAPG Search and Discovery Article #91012©1992 AAPG Annual Meeting, Calgary, Alberta, Canada, June 22-25, 1992 (2009)