An inverse method for calculating basement geometries in foreland basins

Abstract

Flexural plate inversion uses a computer simulation program to model the characteristic patterns of subsidence, deformation, uplift and erosion of basement under sediment load and compressive thrusting. In this modelling it is assumed that lithosphere is an elastic material, which will deform when a force is applied and will return to its original shape when the force is removed. The program is effective in a given geological setting such as a foreland basin formed by compressive thrusting. The program is an inverse model which employs both non-linear least squares and linear search techniques to determine the best values of flexural parameters. Therefore, a user can set a dynamic range for the sizes of input parameters, based on geological and geophysical data, to understand the influence of these parameter changes on the evolution of a foreland basin. In this system, input data include a profile of the present-day basement. The parameters which determine the deformation of the basement consist of flexural rigidity ( D), horizontal compressive force ( P), bending moment ( M 0), applied initial load ( V 0), the dip angle (θ) and the “added length” ( L) of the basement. The outputs are a profile of the deformed basement configuration, which matches the present day basement and also a section of unloaded basin which represents the basement configuration prior to any sediment or thrust loading in the section. The results of synthetic data tests and real data from the Po Basin, Italy show that this system can be used to assess the evolutionary processes affecting a basin under compressive thrusting.