Abstract
An inverse elastic flexural model for foreland basins has been developed and applied to southeastern Sicily. The model employs a non-linear least squares technique to determine the best values for the flexural parameters based on geological and geophysical data, thus avoiding the trial and error approach to parameter determination inherent in forward models. The lithosphere is assumed to act as an elastic plate of finite lenght ( L) and constant flexural rigidity ( D). The plate is anchored at one end in cantilever fashion. Four boundary conditions are necessary for solution of the governing flexural equation: at the fixed end the displacement is zero and the dip angle of the plate is π; on the free end the bending moment is M and the applied load is V. Thus, the plate profile is determined by five parameters, D, L, π, M and V. The model allows for differential lateral loading along the plate, a significant improvement over previous models which assume that the thrust/sediment load is applied at one point at the end of the plate. Sensitivity analysis of parameter determination and uncertainty are also discussed. Cross sections from southeastern Sicily are modeled and in every case the average difference between predicted and observed values is less than 6% of the maximum relief of the basin. The close fits indicate that the subsidence in the region is largely due to elastic flexure of the basement in response to thrust and sediment loading. The results support the contention that two separate basins have developed independently in the region: the Caltanissetta basin, a foredeep depression, and the Ragusa basin, a marginal sag basin. Parameter sensitivity analysis indicates that these two basins have evolved by different tectonic mechanisms. The foredeep is a dominantly flexural basin, while the Ragusa basin has a strong component of isostatic subsidence. In addition, the parameter values and sensitivity patterns are consistent with independent geological information from the region.
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