Subsidence analysis in the Paris Basin: a key to Northwest European intracontinental basins?

Due to the frequently observed disparities between stretching amounts obtained from faults, crustal thickness and tectonic subsidence, the development of intracratonic basins cannot always be explained by a simple model of lithospheric extension. Basin evolution may then be regarded as the result of superimposed and successive processes. The Paris Basin is chosen as a type example for the discussion of European intracratonic basins. The tectonic subsidence, reconstructed using a standard method, is small (maximum of 1600 m, mean rate of 8.5 mm/ka). The long-term linear or concave curves are interrupted by periods of short-term acceleration and deceleration. Thus, tectonic subsidence is clearly discontinuous and five phases, with duration of 20-60 Myr, constitute the long-term Meso-Cenozoic Subsidence. The boundaries and pattern of each phase are identical all over the basin. Subsidence is interpreted as the result of several modifications of the lithospheric . The uniform stretching model can explain the first Triassic to early Liassic phase, the only one with a concave-upward trend (deceleration). The Jurassic to Cretaceous subsidence could be explained by superposing (1) a long-term component caused by lower crustal flow and/or underplating and (2) several short-term accelerations (convex-upward trend) related to compressive or transpressive forces. Geophysical control is insufficient to test the first postulate accurately and the generation of sufficiently high compressional stresses during the Jurassic-Cretaceous is questionable for the second. Other Northwest European basins are compared with the Paris Basin. Although similar features can be observed, the overall image is not uniform: 'Paris Basin' (intracratonic) as well as 'Celtic Sea Basin' (passive margin) signatures, variable long-term trends, lack of synchronism of subsidence phases. This picture necessitates different driving mechanisms for subsidence across Northwest Europe. The variable subsidence patterns and processes result from the 'remote' geodynamics of the Atlantic and Tethyan realms, combined with mainly 'active' processes similar to those proposed for the Paris Basin.