Salt features of France

Emphasis is placed on the genetic-interpretational aspect of the Aquitanian diapirism and its close association with the various orogenic phases of the area under review. The fundamental problem is whether we are concerned with a phenomenon of buoyancy or if purely orogenic forces account for the accidents observed. There is sound evidence that some diapiric accidents occurred as early as middle Cretaceous, independent from and definitely preceding the earliest orogenic phase of folding. On the other hand, there is little doubt that the evaporites of the Keuper furnished a gliding horizon that greatly facilitated disharmonic folding, thrusting, and detachment from the substratum in the course of the Pyrenean orogeny. The author concludes that at an early date, buoyancy was an important active force indeed; later the results of orogenic deformation were superimposed onto the early diapiric structure; the combined effect, as presently in evidence, tends to obliterate the early diapirism.