THE POST-SEDIMENTARY CHARACTER OF DEVELOPMENT OF INTRAPLATE DISLOCATIONS AS A REFLECTION OF IMPULSIVENESS OF DEFORMATION PROCESSES

Abstract

The available data on well-studied areas of the Turan platform (as an example) are reviewed and analyzed to reveal the role of con-sedimentation and post-sedimentation tectonic movements in formation of dislocations of the sedimentary cover. At the background of the long-term (tens and hundreds of million years) quiet evolution of the territory under study, short-term intervals are distinguished, which duration amounts to the first millions of years (typically manifested in one or two stratigraphic layers); in such time intervals, tectonic movements were dramatically boosted and accompanied by land uplifting, sea regression, erosion of sediments accumulated earlier and manifestation of deformation processes.The paleotectonic reconstructions show that during such ‘revolutionary’ stages, large tectonic elements occurred along with local uplifts that added to their complexity. In the region under study, the Pre-Jurassic, Pre-Cretaceous (Late Okoma), Pre-Danish and the Pre-Middle Miocene gaps in sedimentation are studied in detail. It is shown that only during the above four periods of sedimentation gaps and accompanying erosion-denudation processes, the regional structures gained from 50 to 80% of their current amplitudes at the bottom of the cover, and the Pre-Danish and Pre-Middle Miocene washout periods were most important.Local uplift also developed impulsively and primarily due to the post-sedimentation movements. Cross-sections of anticlines studied in detail (Figures 1 to 3) are discussed as examples that clearly show the increase of erosional shearing of the sediments accumulated earlier towards domes of uplifts without any con-sedimentation decrease of their thicknesses. During these periods of the geologic history, regardless of their short duration, folded dislocation gained up to 65–90% of their current amplitudes. The periods of activation were separated by long relatively quiescent tectonic periods with the gradually slowing down growth of anticlines to complete cessation.Dislocations in other regions, such as the Azov Sea (Fig. 4), the Dnieper-Donets basin, Donbas, etc. were formed under a similar scenario.Impulsiveness of tectonic processes is well illustrated by events that recently took place at the Taman peninsula. In 2011, the sea bottom uplifted dramatically along the coastal line of the Azov Sea and formed a new land segment (Figures 5 to 8). The vertical movement amplitude amounted to minimum 5 metres. This new structure formation was due to a short-term renewal of growth of the Kamenny Cape. After the short-term activation of tectonic movements, the period of tectonic quiescence is in place, and the majority of the uplift has been destroyed by marine erosion.Impulsiveness of tectonic movements may be caused by the tangential stress that periodically puts an impact on the lithospheric plates. Horizontal tectonic movement and associated stresses can lead to both interplate and intraplate deformations.

Keywords

• dislocations
• sedimentation gaps
• tectonic impulses
• stress release