Les regressions marines et le probleme du renouvellement des faunes au cours des temps geologiques

Abstract

One basis for geochronology is the succession of faunal groups. Evolutionary transformations, the extinction of species, and the appearance of new forms is neither a chance occurrence nor one marked by a regular rhythm. The disequilibrium provoked by alternating transgressions and regressions has a profound effect on animal populations. At the end of each marine regression a hecatomb of fauna is left in the neritic zones. A return of the sea in the succeeding transgression provides opportunity for the multiplication and diversification of the surviving forms. Through this process of natural selection evolutionary development is stimulated by alternating marine cycles.