Some observations on basin evolution and dynamics

Abstract

Sedimentary basin evolution is intimately bound in with continental lithosphere dynamics. Deep seismic reflection profiling has revealed images of the crust and upper mantle that suggest linkages between the shape and structure of sedimentary basins as they evolve with the rheological responses to tectonic stress of upper and lower crust and upper mantle components of the lithosphere. This is well illustrated by the European Geotraverse lithosphere profile from North Cape, Norway to Tunisia. The Alpine mountain belt has a lithospheric root as well as a crustal root. By virtue of its asymmetric disposition, this may be the cause of compressive and tensile forces in close association in the upper crust, which have created mountain uplift and basin subsidence, extension and thrusting, all in juxtaposition. Evidence for an elastic upper layer of crust above a plastic substratum can be used as a basis for modelling basin geometry, structure and stratigraphy built upon the flexural nature of the upper crust. Such models go a long way towards simulating the evolution of basins such as the North Sea Viking Graben. In more detail, analogue structural models can reveal the geometry of basin fill in relationship to crustal movement, and the relationships between structure and sedimentation patterns. However, sedimentary basin modelling needs to begin with the quantitative simulation of depositional environments in relation to such factors as tectonics, sea level variations, sediment supply and erosion, in order to match sedimentary architecture. Only then can the range of deposits be placed in space and time within a basin environment, as building blocks within a dynamically evolving structural framework, to create predictive models for comparison with geological reality.