Geodynamics and Basin-Forming Mechanisms in the Provencal Basin: A Modeling Discussion: ABSTRACT

Abstract

The Provencal basin is part of the Western European rift system created in Oligocene time; it has reached the oceanic stage as a result of the eastward drifting of Corsica and Sardinia. It is a well-documented example of a young extensional basin. Good-quality seismic refraction and reflection data as well as heat-flow determinations show that the basin presents many characteristics commonly observed in an extensional basin: (1) a distinct synrift structure associated with graben formation, minor block tilting, and very small horizontal extension (< 10%); the end of the synrift phase is marked by a well-defined unconformity; (2) significant crustal attenuation visible in both the upper crust and lower crust; the average vertical thinning (1.9) is by far more important than the horizontal extension (1.1 to 1.3 ); (3) asymmetric structure of the conjugated Corsican-Sardinian/provencal margins, associated with asymmetric heat flow and Bouguer profiles. As a consequence, the classic stretching mechanism or the simple shear model does not apply to the observed geometries. The paradox is that the stretching concept adequately accounts for the distribution of the heat flow and for the subsidence (after correction for recent compression). Alternative basin-forming mechanisms will be discussed in terms of crustal metamorphism andmore » ductile flow.« less