ГЕОДИНАМІКА

Abstract

The article focuses on the formation mechanisms of fold’s diversity of sedimentary basin inversion. They are investigated on the example of structures of the Dnieper-Donets paleorift system. To achieve this aim we systematized structural and lithofacial data of the Dnieper-Donets basin and Donbas; used numerical modelling to establish the regularities of deformations within lithosphere and sedimentary cover in collisional compression setting. It is shown that the formation of main folding styles as discontinuous (intermittent), transitional and continuous (full) is accompanied by characteristic features of the cover. In this respect, we formulated the basic dependence principle of folding from lithofacial and lithogenic factors, which defined different mechanical properties of sedimentary cover complexes (the lithomechanics principle). Modelling results confirm prime significance of horizontal compressional conditions of basin’s folds development. Moreover, the sedimentary basin plays the role of independent deformation attractor in the lithosphere. The main conclusion is that the transitional fold paragenesis of Donbas with crest-like Main anticline may be the result of particular strength’s distribution, i.e. axial weak zone and competent layer of variable thickness with central minimum. Main anticline formation mechanism is complex. It includes vertical, axial-parallel viscous-plastical flow with distant bending. It is shown that intermittent folds (uplifts) of the Dnieper-Donets basin may be a result of sedimentary cover compression with a random combination of weakened and strengthened zones. On the contrary, full folding of East Donbas and the Karpinsky ridge corresponds to a bending mechanism of competent layer compression of constant thickness. For the first time we obtained the evidence for the folding inversion mechanisms within Dnieper-Donets aulagogen (including Main anticline), which was problematic for many years. Folding is directly related to peculiarities of sedimentary basin infilling within formulated principle of lithofacial mechanics. With necessary caution, the study offers the results of modelling and conclusions for explanations of fold development within intracontinental basins and marginal folded belts. Practical significance. Numerical modelling and elaborated principles of analysis may be used in reconstructions, numerical investigations of fold structures (uplift) within inverted basins, as well as in prognosis of ore, oil-and-gas deposits.