On mega-undations: A new model for the earth's evolution

Abstract

Two fundamentally different views on the origin of the sialic crust of the earth are possible. According to one view the sialic crust has been produced from the inside by progressive physico-chemical differentiation of the earth's material into concentric spheres. Such an endogenic origin of the crust is supported by most contemporaneous geological theories. According to the other view the crust has been acquired from the outside, shortly after the earth's agglomeration, as an outer layer of more acid satellitic material. This exogenic origin of the crust is suggested by Berlage's theory on the origin of the planetary system. In this paper it is attempted to test Berlage's astronomical theory by means of geonomical facts. It appears that the postulate of the acquisition of the crustal matter from the outside leads to a satisfactory theoretical model of the earth's evolution. Three major phases can be distinguished: 1. (I) The acquisition of an acid layer from without. 2. (II) Its transformation. 3. (III) Its incorporation (see Fig.1). An important aspect of this model is that it provides a synthesis of the two main trends in the geological thought of our time, the fixistic concepts (recently represented, for example, by Subbotin et al., 1965a,b,c), and the mobilistic concepts (recently represented, for example, by Blackett et al., 1965). This synthesis is obtained by means of the relativistic principle in the analysis of the crustal movements and deformations. The effects of the causative mass displacements at various depths, and occurring at various times, are superimposed on each other. The processes in depth produce in combination the structural phenomena observable at the surface. The Alpine cycle of orogeny is analysed according to this relativistic principle (Fig.3). The influence of mega-, geo- and meso-undations can be distinguished. The mega-undations are generated in the lower mantle. They cause the “Tethys-Twist” and the continental drift, which is accompanied by mega-shears and the formation of new ocean basins (Atlantic type of oceanization). The geo-undations are related to physico-chemical processes, which occur in the upper part of the upper mantle (the asthenosphere). They result in the formation of eugeosynclines, accompanied by ophiolitic magmatism (the eugeosynclinal phase). Thereafter, centres of orogeny are formed in the geosynclinal area by subcrustal mass circuits, which corrode the crust from beneath (Mediterranean type of oceanization). By this penetrative type of convection, the overlying crustal matter (covered by geosynclinal sediments) is rafted outward from these centres. Meanwhile migmatized sialic matter is injected sidewards into the flysch foredeeps. This tectogenesis produces nappe structures of East Alpine and Pennine character (flysch phase). Finally, an isostatic equilibration of the matter that accumulated in the foredeeps produced meso-undations, namely the uplift of the Alpine mountain ranges and the subsidence of sidedeeps (molasse phase, see Fig.4 and 5). An analysis of the present picture of the structural features of the earth (Fig.6) confirms the concept that the seemingly opposed mobilistic and fixistic mechanical models should be combined into a synthesis of relativistic character. During the third phase of the earth's geological evolution (the last half billion years of its history), the sialic crust is progressively incorporated into the upper mantle by means of the Mediterranean type of oceanization. The crustal fragments thereby acquired a greater freedom of movement and they started drifting towards the Pacific area (Pacifico-petal drift), opening new oceanic basins in their wake (the Atlantic type of oceanization). The expectation of this relativistic model of the earth's evolution appears to conform to the diagnostic data of the post-war geonomic researches, so that this hypothesis deserves further elaboration and testing.