DNIEPER-DONETS BASIN, UKRAINE - MAIN OBSERVATIONS FROM REGIONAL SEISMIC-REFLECTION PROFILES

In any transverse section of the Dnieper-Donets basin the rift, filled with pre-rift and syn-rift Devonian sequences, overlain with post-rif t Carboniferous, Permian, Mesozoic, and Palaeogene fill, is explicitly expressed. Within the rift boundaries the crystalline basement is ove rlain with Devonian sediments, while the shoulders are overlain by Car boniferous strata. The structure of the rift is characterized by large -scale rotational fault blocks and half-grabens, carried by the basin- parallel to normal marginal faults or by major horst blocks. The rift is conjugated with its shoulders mainly along large-amplitude normal f aults. The main stage of Devonian rifting occurred during the Frasnian and Famennian. Post-rift basin development is characterized by the fo rmation of a vast syncline, set on the rift and its shoulders, commenc ing in Tournaisian time (362.5 Ma). Carboniferous and Mesozoic sedimen ts cover the rift flanks and increase in thickness towards the rift ax is. Maximum thicknesses of the successions occur in the southern part of the axial zone of the basin and in the Donbas. The cumulative thick ness of the Carboniferous sediments reaches 11 km, with the maximum de pth of their base at about 15 km. The maximum thicknesses of sediments , accumulated during the whole Late Palaeozoic and Mesozoic history of the DD basin, constitute 2-6 km to the northwest and 15-19 km to sout heast and in the Donbas. The axis of the maximum post-rift subsidence practically did not change its spatial position. Major post-rift tecto nic events took place between the Devonian and Carboniferous, at the e nd of the Early Visean, in the middle of the Serpukhovian, between Ear ly and Middle Carboniferous, in Permian time, and between the Mesozoic and Cenozoic Tectonic reactivations during the entire Carboniferous, Early Permian and the end of Mesozoic time were most pronounced in the southeast part of the DD basin and in the Donbas, whereas they were l east pronounced in the northwest part of the basin merging the Pripyat Trough where they are barely observed. The most active development of salt structures and stocks correspond with the periods of structural reactivation.