THE FORMATION OF THE SOUTH-EASTERN PART OF THE DNIEPR-DONETS BASIN: 2-D FORWARD AND REVERSE MODELLING TAKING INTO ACCOUNT POST-RIFT REDEPOSITION OF SYN-RIFT SALT

Abstract

Forward and reverse modelling of structure and stratigraphy has been used to investigate the syn-rift (Late Devonian) and early post-rift (Carboniferous) evolution of the south-eastern part of the Dniepr–Donets Basin (DDB). Modelling was carried out with and without taking into consideration the withdrawal and surface extrusion of Devonian salt during the formation of salt diapirs. The great thickness of Carboniferous deposits can be explained by the superimposed actions of three processes: post-rift thermal subsidence, withdrawal of Devonian salt from the mother layer during phases of salt diapir activity, and regional subsidence of the East European Platform. The effects of other tectonic and/or non-tectonic processes are not required.Forward syn-rift modelling using the flexural cantilever model of sedimentary basin formation predicts the total syn-rift extension across the southeastern DDB to be approximately 65 km with a maximum β stretching factor of 2.4. Shallowing of the Moho during the syn-rift phase is estimated to be 15 km. The present-day Moho, after thermal subsidence and basin fill, is predicted to be 4–6 km shallower than surrounding regions.In the axial zone of the south-eastern DDB the thickness of the Devonian syn-rift sequence may have reached 7.5 km by the end of the rift stage. This is 3–3.5 km more than at present. The thicknesses reduction is due to the outflow of Devonian salt during post-rift periods of halokinetic activity in the early Visean, the middle Serpukhovian, and in the Early Permian. The withdrawal of salt from the mother layer produced additional accommodation space and up to 1.5–1.7 km of the total eventual thickness of the Carboniferous sedimentary succession can be explained as a result of this.