Flexural Modeling of Sedimentary Basins

Jeffrey C. Cogan, Ian Lerche

Basement response to loading is of primary importance in the evolution of sedimentary basins, strongly influencing both the thermal and burial histories of the sediments. The presence of regional free-air gravity anomalies over large-scale features suggests that surface loads are not completely compensated by isostatic forces. Therefore, one must consider the role of nonisostatic lithospheric flexure in dynamic basin modeling.

The basic assumption of the model is that the lithosphere behaves like an elastic thin plate of finite length, anchored at one end in cantilever fashion. In the forward mode, the loading history and plate parameters (flexural rigidity, initial length, initial dip angle, initial bending moment) are specified and the resultant basin geometry is calculated. However, this approach gives only a rough estimate of the plate parameters for a particular basin. Therefore, the model is inverted, employing a tomographic scheme to determine the parameters that best fit the data. This model yields tighter constraints on the plate parameters, hence a better knowledge of basement motion through time.

The model can be used to determine the relative importance of flexure vs. isostatic subsidence in an individual basin as well as the sensitivity of basement motion to the various flexural parameters.

AAPG Search and Discovery Article #91030©1988 AAPG Annual Convention, Houston, Texas, 20-23 March 1988.