LICKORISH, HENRY, Geologica AS, Stavanger, Norway; MARY FORD, Ecole Nationale Supérieure de Géologie, Institut National Polytechnique,Vandoeuvre-Les-Nancy Cedex, France

Abstract: Corellation of foreland basin stratigraphy to tectonic deformation, constraining the 3D evolution of fold and thrust belts. An example from the Western Alps.

Association of foreland basin stratigraphy to tectonic deformation in balanced cross-sections constrains timing of both local and regional structural and stratigraphic evolution. Along-strike variations can therefore evaluate the 3D evolution of the foreland basin/thrust-belt system.Variations associated with the 90° change of strike in the regional structure of the western Alpine arc, and foreland basin serve to illustrate this.

Similar timing and styles of deformation are observed in both the SW Alpine foreland basin (SWAFB), and the north Alpine foreland basin (NAFB), with separate linear flexural, asymmetric nappe-overthrust, and radial basement uplift phases. Similarity of tectonic styles is reflected in the foreland basin, which evolves from linear to highly asymmetric before developing the final, more symmetric radial system. The Eocene basin, common to both the NAFB and SWAFB, palinspastically restores to have a low curvature suggesting that it predated arc development. Oligo-Miocene overthrusting of nappes produced negligible further subsidence in the SWAFB. However, the NAFB accommodated over 4000m of sedimentation while remaining approximately 50km wide.This asymmetry is a result of a change of tectonic regime in the internal Alps, and collision with the Adriatic indentor, which developed the curve of the Alpine arc, and isolated the SW Alps from any major crustal shortening changes. In contrast, Late Miocene and Pliocene basement uplifts are more symmetrically placed with a strike which matches the inherited curvature. Pliocene deformation along the thrust front interacted with the extensional basin systems of the Rhone and Bresse grabens controlling the basin style.

AAPG Search and Discovery Article #90923@1999 International Conference and Exhibition, Birmingham, England